The Italian navy’s 10th Light Flotilla had been waging its own clandestine small war on the peninsula, mounting nine operations in three years against Gibraltar. As we have seen in Malta, Decima Flottiglia MAS, the Italian navy’s or Regia Marina’s assault craft branch, had developed revolutionary new weapons and tactics: midget submarines, explosive motorboats, piloted torpedoes, swimmer-frogmen with ‘leech’ or ‘limpet’ mines, all of them technologies later copied by other navies in the Second World War.

At two o’clock in the morning of 30 October 1940, a curiously shaped submarine surfaced in the dark lapping waters at the north end of Algeciras Bay. This was the commercial anchorage, opposite La Línea, near Puente Mayorga and the mouth of the Rio Guadarranque, a couple of miles from the entrance to Gibraltar harbour where the British warships lay. Scirè, an Adua-class Italian submarine commanded by Junio Valerio Borghese, looked very odd. It seemed to have larval cases attached to its hull, three long ribbed cylinders, one for’ard in place of a deck-gun, two aft of the conning tower. The submarine also had ‘distractive’ camouflage painted on its grey hull, the dark shape of a trawler with its bow pointing towards the sub’s stern.

Scirè had made its way through the Strait of Gibraltar the night before, then hovered seventy metres underwater all day, banging on rocks in the Bay of Tolmo halfway between Tarifa and Algeciras. Only when darkness fell did Scirè creep slowly and silently into the bay between Algeciras and Gibraltar, under the cover of a moonless night. The currents were tricky because of reefs and sandbanks, but Borghese was following the tidal flux that flows into the bay from the southwest.

Looking east, the periscope view had shown Gibraltar brightly lit up; sometimes searchlights played over the water. When submerged in the bay, the submariners tiptoed in rope-soled shoes, spoke in whispers or sign language, wrapped their tools in cloth so no ‘clang’ could alert enemy listeners above them. Deep under water, their hydrophones could pick up engine noises on the surface: motorboats, Spanish trawlers, a British destroyer.

When they surfaced, the hatch opened to the cool night air and six men, wearing tight-fitting black rubber frogman suits that left only their hands and faces exposed, made their way to the three cylinders on the submarine’s deck. They opened the doors and rolled out the torpedoes or SLCs stowed inside. SLC stood for their official name, Siluro a Lenta Corsa, ‘slow speed torpedo’, but their Italian operators called them maiali, ‘pigs’ or ‘hogs’, because sometimes they were hard to steer properly. An operator cursed it, ‘Maiale!’ and the epithet stuck. The British name for them was ‘chariots’.

The maiali were manned torpedoes, 6.7 metres (nearly twenty-two feet) long, weighing 1.3 tons, with an electric motor and a propeller at the back. They were ridden underwater by two operators astride with their feet in stirrups, the officer in front steering and the NCO at the back ready to cut anti-torpedo nets and use tools. The whole rounded front of the ‘hog’ torpedo was a detachable warhead, containing three hundred kilos of explosive and a time fuse. On top of this warhead was a suspension ring through which a rope could be threaded. The mission consisted in getting close to a ship, then diving underneath it and attaching clamps to either side of the bilge keel, a ledge that runs round the bottom of a ship. The tricky task then was to hang the heavy warhead on a rope looped between the two clamps, so that the explosive was dangling directly below the keel when it blew up.

The operators put on goggled face masks with a single corrugated tube connected to the rubber breathing bag on their chests. This contained a canister of soda lime crystals which ‘scrubbed’ the carbon dioxide from their exhalations, while pure oxygen was delivered from pressurised bottles strapped horizontally across their bellies.

The six men mounted their ‘hogs’ and Borghese submerged the submarine, which crept southeast out of Gibraltar Bay and stayed underwater for the next forty hours, returning through the strait. When they finally surfaced, gasping for air, Borghese could see the sun setting behind Gibraltar on the western horizon, ‘the great rock, crouching like a lion on the sea’.

Now the brave men astride their ‘hogs’ were left on their own to attack their assigned targets. The first pair, De La Penne and Bianchi, were depth-charged by a motorboat, which sank their torpedo. They abandoned their breathing gear, swam two miles to the Spanish shore and met their agent, retired naval officer and engineer Giulio Pistono, at the prearranged spot on the road at 7.30 a.m. An equipment failure in their breathing gear also scuppered the second pair, Tesei and Pedretti, although they got within sight of Gibraltar’s North Mole. They too turned for Spain, detached the warhead after fifteen minutes, and headed north for the western lights of La Línea, the district known as La Colonia. They landed at 7.10 a.m. and Tesei opened the flooding tank of the torpedo and sent it off southwards. It did not sink, eventually coming ashore at Espigon Beach, La Línea, with its propeller still whirling, where the Spanish authorities took it away for examination. By then the operators had shed their diving suits and met up with their agent, Pistono, who arranged for all four men to get to Seville and fly back to base in Italy.

The last pair, Gino Birindelli and Damos Paccagnini, got into Gibraltar’s harbour and within seventy metres of the battleship HMS Barham before their craft became immobilised on the bottom. Paccagnini’s breathing apparatus had failed too, so he was sent to the surface. Birindelli set the time fuse on the warhead and tried to swim back to Spanish territory but, attacked by ferocious cramp, he had to crawl out of the water onto the North Mole. He managed to mingle with Spanish dock workers, got on board a ship called Sant’Anna and tried to hide.

When the crew found him they said they were under Contraband Control and that no one could leave without British permission. Birindelli offered a bribe of two hundred pesetas; they were about to take it when a British sailor came on board and asked if Birindelli was one of the crew. When the men hesitated, the British sailor came back with two policemen, who arrested Birindelli and took him for questioning by a naval officer. He showed his Italian identity card and the astonished lieutenant immediately summoned a commander. Meanwhile, the sunken warhead exploded with a monstrous gout of water, lightly damaging Barham and setting the whole harbour in a flutter. Paccagnini had also been picked up and both frogmen became prisoners of war.

In a coded letter to ‘his family’, Birindelli urged his ‘brother’ to make another effort ‘to get his university degree’. ‘If at first you don’t succeed, try, try again; if one makes the proper preparations, one finds the difficulties are not insuperable.’ The 10th Light Flotilla got the coded message, and tried again in May 1941.

This time, to keep the operators fresh, not cramped in a stuffy submarine, it was decided to send the eight men overland to Cádiz, where a six-thousand-ton Italian tanker called Fulgor had been interned since June 1940. Pretending to be variously members of the crew or representatives of the owners, they got on board and waited for the Scirè to pick them up for the final run to Gibraltar. The submarine berthed nearby on 23 May; its crew got hot showers aboard the tanker, restocked with fresh fruit and vegetables and generally stretched themselves out, unbothered by the Spanish authorities. Someone from the Italian Consulate in Algeciras gave them all the latest intelligence from his recent reconnaissance of Gibraltar.

Just before midnight on 25 May 1941, the Scirè surfaced in Algeciras Bay and three ‘hogs’ were released. Gibraltar’s harbour by now was more heavily guarded, so their targets this time were ships in the commercial anchorage. One of the ‘hogs’ failed straight away, so the riders detached the warhead and got another torpedo to tow it. Each ‘hog’ now had three crew. At the first ship they targeted, one of the operators lost consciousness, possibly through oxygen poisoning or hyperoxia which affects the eyes and the central nervous system, and in rescuing him the other two let go of the torpedo, which sank irrecoverably in deep water; the men swam for the Spanish shore. The crew of the third ‘hog’ were attaching a warhead when the rope snapped and that torpedo was lost too. But the six men all got ashore undetected, a car took them to Seville and LATI (Linee Aeree Transcontinentale Italiane) flew them home.

On 20 September 1941 they tried again. Operation BG4 had the same routine: pick-up from Fulgor in Cádiz, ride in Scirè to Algeciras Bay, three two-man crews on their ‘hogs’, the escape team waiting in Spain. This time each of them scored. First the 2400-ton Shell oil storage hulk Fiona Shell was cracked in two and sank. Then at 8.43 a.m. the 15,800-ton naval tanker Denby Dale blew up, followed by the 10,800-ton freighter Durham at 9.16. The perpetrators all got away safely. Rumours reached Defence Security on the Rock that some of the divers had been arrested by the Spanish carabineros but had then been ‘sprung’ by the Italian naval officer Giulio Pistono, who had acquired diplomatic status as ‘Chancellor’ at the Italian Consulate.

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Now Gibraltar had to wake up to the danger of underwater attack. The Royal Navy Extended Defence Officer started using his three harbour launches to drop light depth charges on their regular night-time patrols of the anchorage, inspecting Spanish fishing vessels and sweeping the water and the sides of ships with their searchlights. Three months later, startling news reached the Rock from Egypt. In their greatest success, Italian frogmen from Decima Flottiglia MAS had managed to penetrate Alexandria harbour, plant mines and blow up the British battleships HMS Queen Elizabeth and HMS Valiant. Vigilance in Gibraltar was increased.

The Italians came up with an even more ingenious scheme. Why travel all the way by submarine from Italy to attack Gibraltar? Why not set up a base close by in Spain? The first step was purchasing properties. Pistono already lived at a house called Buen Retiro in Pelayo. The Italians acquired another house in the smart part of La Línea, La Colonia, at 98 Avenida de Espana, which had an excellent view of Gibraltar’s commercial anchorage, the North Mole and the Coaling Arm. Then they rented the Villa Carmela in Puente Mayorga from a Spanish estate agent acting for its Gibraltarian owner, J. L. B. Medina, who had been evacuated to Madeira. Antonio Ramognino and his new Spanish bride Conchita took up residence. Their honeymoon treats included adding a new window for telescope and binocular surveillance, screening activities behind the glass with a cage of screeching parakeets.

The actual secret base for the frogmen was the Italian cargo ship Olterra which, as we have seen on page 190, was scuttled unsuccessfully on 10 June 1940, the day Italy entered the war. A Spanish salvage company had refloated the ship and towed her into Algeciras harbour where she was now moored inside the breakwater, south of Isla Verde and more or less right under the windows of the British Consulate. A Spanish military guard consisting of a corporal and three privates, and occasionally visited by a junior officer, was stationed aboard with orders to let no boats near and allow no foreigners or civilians to enter the ship unless they were crew members with special passes. Since March 1941, the chief engineer and a scratch crew formed from other vessels interned in Spanish ports had been living on board, maintaining the vessel (and protecting property rights under international wreck and salvage law). The skipper, Domenico Amoretti, had married a local girl and lived ashore in Algeciras.

Early in 1942, Lieutenant Licio Visintini of the 10th Light Flotilla, the man who was on the maiale that sank the tanker Denby Dale in Gibraltar harbour on 10 September 1941 and brother of the dead fighter-pilot air ace Mario Visintini, was put in charge of the clandestine Olterra operation. The first thing Visintini did was purge the crew already on the ship and replace them with technicians and seamen from his own unit. They were sent to Livorno to live aboard a cargo ship and learn ‘deck technique’: how to walk, talk, smoke, spit and dress like Italian merchant seamen, scruffy, unshaved, in old patched clothes. With fake names, identity cards and log-books (but using their real passports) they made their way to Spain to join the ship and ‘effect repairs’.

In fact, deep in the hold, they were building an entire submarine workshop, capable of charging the accumulator batteries and assembling the ‘hogs’ that would soon be arriving in bits. They prepared a compartment in the forepeak that was deep enough to trim the torpedoes and test them for water resistance. Then they started careening the ship, which had a list and was already down at the stern. One afternoon a large area of the port-side hull was raised above the water, and an awning was rigged to protect the workers from the sun (and any watchers from the British Consulate). There was lot of hammering and painting and scraping, but those workers were also there to mask and catch the sparks produced by another crew, inside the ship, who were using an oxyacetylene torch to cut a four-foot-square hinged hatch in the hull. By nightfall, with the ship’s trim adjusted, there was an underwater exit and entrance from the flooded compartment, invisible, six feet below the waterline.

In the main base at La Spezia in Italy, the torpedoes were being broken down into sections and crated as the sort of spares required to repair a ship’s engines and boilers – tubes, pistons, cylinders, valves, etc. The breathing sets were hidden in containers welded into the bottom two thirds of drums of diesel that carried enough fuel at the top to deceive any Spanish custom officer’s probing dipstick.

In dribs and drabs, the torpedo pilots came on board ship, also disguised as seamen and workers. Leaning casually over the rail, they were actually studying the anchorage, the regularity of the patrols, the depth-charging, the movements of sentries, the procedures for entering and leaving harbour. Their doctor, Elvio Moscatelli, even went into Gibraltar with a donkey cart, selling fresh fruit in the dockyard, in order to look at the precautions that were being taken against divers. Through the porthole of an Olterra cabin he organised a twenty-four-hour watch of Gibraltar harbour, recording everything. They also spotted that on the balcony of the British Consulate behind them there was a superb set of binoculars, mounted on a tripod. One night the binoculars vanished, and Olterra gained sixty-four times magnification.

An elaborate pretence of normality on Olterra – systematic work routines, regular clockings in and out, standard deliveries – masked the project and kept it secret from the Spanish. The Spanish guards on board were lulled and gulled by a skilful new cook, generous with the vino, who kept them well fed aft, leaving the works down in the bowels of the bow undisturbed. And British intelligence across the water in Gibraltar were also fooled.

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In June 1942, a new intelligence officer called Desmond Bristow arrived in Gibraltar. Bristow spoke fluent Spanish because he had grown up in Spain, where his father ran one of Rio Tinto’s mines near Huelva, and he had been working on the Iberian desk of Section V, SIS Counter-intelligence, in St Albans, alongside Philby and Milne. Desmond Bristow’s companion on the journey out to the Rock was another Spanish-speaking SIS man, the former priest Aelred O’Shagar.

The new men had to fit in with the Gibraltar intelligence community already crammed into a flat-roofed building in Cloister Ramp behind the police station in Irish Town. Here the Defence Security Officer, Lieutenant Colonel H. C. ‘Tito’ Medlam, with his four staff, worked assiduously to protect the Rock from espionage and sabotage. Here too beavered away Lieutenant Colonel John Codrington of MI6 and his assistant Brian Morrison, whose job was watching the Spanish armed forces for aggressive intentions. Over in another corner was Donald Darling of MI9, handling his evaders and escapers. Now Bristow and O’Shagar of Section V squeezed in.

Because their task – keeping track of German and Italian intelligence personnel and their agents working in the Campo de Gibraltar – overlapped with the work of both the DSO and MI6, the new men were not immediately popular. Medlam had to pass on his counterespionage files and some informants, including a pair of brothers in the Campo, F1 and F2, whom Bristow called ‘the Josephs’. On grounds of Irish solidarity, O’Shagar tried to milk as much information as possible from the office clerk, Corporal Kevin Cavannah. Bristow soon moved into a shared third-floor flat in Plaza de la Verdura with Darling and Morrison, where they listened to jazz records and drank heavily. (Espionage and alcohol, as ever, walked hand in hand.)

Desmond Bristow cultivated whisky-drinking Biagio D’Amato, one of the brothers who ran the successful Café Universal and Embassy Club in Main Street. The Maltese Gibraltarian was a source of much interesting information as well as free drinks, and was valuable to the new members of the intelligence community when they were still scrabbling to get their own agents, contacts, ‘cut outs’ (mutually trusted intermediaries), informants and sources. But none of the intelligence officers knew what was going on aboard the Olterra across the bay.

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In early July 1942, twelve strong assault swimmers from the Italian 10th Light Flotilla ‘Gamma’ group were smuggled into Spain from Italy. Six went via Bordeaux and crossed the Pyrenees either on foot or hidden in the false bottom of a lorry. Another six went as crew on a cargo ship to Barcelona, where they ‘deserted’ and were reported as such by the skipper, who was not in on the subterfuge. Helped by Italian agents, the swimmers were funnelled via a safe house in Madrid down to Cádiz and the Fulgor, before being smuggled to Algeciras by different routes. They reached the Olterra on 11 and 12 July. The ship was not yet fully prepared to be the base for an attack, so at dawn on the 13th they were taken to the Villa Carmela, where they had a good view of the ships in Gibraltar’s commercial anchorage, and could rest on floor mattresses the Ramogninos had prepared.

Operation GG1 was launched that night. The dozen swimmers in their black Belloni shallow-diving suits left the darkened villa, crossed the garden and, concealed by a low wall, made their way down the dry Mayorga watercourse to the beach of the bay between Algeciras and Gibraltar. They put on their fins and their breathing gear, topped by a camouflage head-net of trailing fronds that floated in the water like seaweed. Every man was carrying three Italian limpet mines, known as cimici or ‘bugs’, which each contained about three kilos of explosive. These mines did not rely on magnets to adhere to a ship’s hull, but were set inside something like a child’s swimming ring, a thin rubber tyre that could be inflated by a snapoff phial of compressed air. The physics of lighter air rising to the surface like bubbles through water would push the ring upwards, so it had to be put right under the bottom of a boat to stay in situ, not placed on the ship’s flank where it might slide to the surface and give them away to the British.

The frogmen slipped into the dark water and swam out slowly and quietly, with no splashing, puffing or phosphorescence, into the anchorage. They had to freeze or duck just below the surface whenever the British patrol boats or searchlights went by. One frogman had his foot cut by a passing propeller and another was shocked by the explosion of a depth charge, but those who reached the ships dived down to place their ‘bugs’. All made it back to shore. Seven were arrested by the Spanish carabineros and taken to Campamento, but then the Italian consul, Bordigioni, arranged for them to be only half-heartedly detained in a hotel in Seville. Some of the pneumatic limpet mines failed (and at least one floated to the surface), but early on 14 July, Bastille Day, a series of explosions damaged four British cargo ships in Gibraltar’s waters – the Shuna, the Empire Snipe, the Baron Douglas and the Baron Kinnaird.

Two months later, five assault swimmers struck again. Two newcomers ‘deserted’ in Barcelona, and three others, among the detainees in the Sevilla hotel, traded places with three seamen from Fulgor, without the Spanish apparently noticing. Once again they went from the Olterra to Villa Carmela and then down to the beach. On this night, however, only three swimmers set out. The ships were moored further away from La Línea now, or were actually in the harbour, and the task was harder because they were more closely guarded, with more searchlights, five motor launches aggressively patrolling and even a couple of rowing boats keeping a close watch. Two Italian frogmen nevertheless managed to plant pneumatic mines on the same ship, the 1787-ton steamer Ravenspoint, which sank.

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This incident was a tiny part of a greater toll. 1942 was the worst year of the entire war for British ship losses. Over 350 Royal Navy ships were sunk and more than fifteen hundred merchant navy vessels went down – an appalling loss of 7.7 million gross tons of shipping, with thousands of men killed. In part this was because in February 1942 the German navy’s U-boat command introduced ‘Shark’, the four-wheel Enigma key which British signals intelligence at Bletchley Park could not crack for the next nine months. On the other side, B-Dienst, German signals intelligence, had succeeded in cracking Naval Cipher No. 3, which was used by Britain, Canada and the USA in their Atlantic convoys, and so was receiving a flood of information.

As shipping built up for Operation Torch in late 1942, Gibraltar was determined to stop sabotage attacks in the harbour. Enter the rough diamond Lionel Crabb, whom all his friends called ‘Crabby’. He did not like his nickname, ‘Buster’, because he was not at all like the super-fit American actor Buster Crabbe, who won a gold medal for swimming at the 1932 Olympic Games and went on to play Tarzan, Flash Gordon and Buck Rogers in the movies. (Nor, for that matter, was he much like the Lithuanian Jewish actor Laurence Harvey, who dyed his hair blond to portray Lionel Crabb posthumously in the 1958 British war film The Silent Enemy.) The real Crabb was red-haired, short and stocky. His friends insisted he was not homosexual, but a woman he was married to for a year in the 1950s said they never had sex and he liked to wear a rubber diving suit in bed. Crabb trained on cigarettes and alcohol, disliked physical exercise and was a poor swimmer. But he was a dogged gamecock who did not give up easily and he could endure discomforts that would put off weaker or less courageous people. According to Frank Goldsworthy, the Daily Express reporter who was then an RNVR officer in Gibraltar’s Naval Intelligence Centre, Crabb was ‘a bit of a character’, but ‘a great enthusiast for underwater work, and a great patriot’.

Crabb’s route into the Royal Navy had been roundabout, drifting where the tides of life took him. Knocking about in odd jobs, he had sailed and sold, modelled trusses, pumped gas, been a Chinese calligrapher and a chaperon to an alcoholic. Roman-nosed and red-bearded, looking like a down-at-heel admiral, carrying a swordstick, wearing a jade talisman and mixing with bohemians and gays in the art world, he lived a year in the top floor back of Rosa Lewis’s Cavendish Hotel (paying for it by working as a porter), before sailing as a merchant seaman gunner on a tanker bound for Aruba. He was in the converted trawlers of the Royal Naval Patrol Service at Lowestoft until an eyesight defect – a so-called ‘lazy eye’ – debarred him from sea service.

Lieutenant Lionel Crabb had a shore job in Coastal Forces at Dover when a man he met in a pub got him into dealing with unexploded bombs. Not everybody has the kind of cool-nerved courage needed for this job. Crabb did. Although he could not be bothered with all the scientific theory and technical detail, Crabb eventually washed up in Gibraltar in November 1942 as a mine and bomb disposal officer. Commander Ralph Hancock at the Tower told him about the Italian attacks and said that they now had two divers checking ships’ bottoms for limpet mines. It would be Crabb’s job to dispose of whatever mines and ordnance they brought up. However, on his own initiative, Crabb went to see Lieutenant William Bailey, who with his assistant Leading Seaman Bell comprised the entire diving team, and asked them if they wanted a hand. He learned the divers did not have fancy rubber suits or fins but went down in swimming trunks and overalls with weights attached to their tennis shoes. For breathing they used the Davis Submerged Escape Apparatus, which was really an emergency oxygen rebreather device designed to help trapped submariners to get out of a watery tomb. Bailey and Bell had borrowed sixteen DSEA sets from Captain Fawkes of the submarine depot ship HMS Maidstone but they did not really know how to maintain them by regularly changing the granular crystals used for carbon dioxide ‘scrubbing’.

Crabb did his first dive that November afternoon. He put on ill-fitting goggles, clipped his nose, clamped his teeth on the rubber mouthpiece and tried breathing in and out, inflating the rubberised bag on his chest. Then he climbed up and down a ladder that dropped from the dockside into the water, practising the unnatural process of breathing underwater. He did not want to go all twelve feet to the bottom because he had heard there might be small octopuses there and he hated the thought of their suckered tentacles snaking around his feet and ankles.

Then Lieutenant Bailey took him out in the diving launch to examine a ship. Crabb swam unhandily for the bottom line that depended from the ship and hauled himself down the red hull to cling to the ledge of bilge-keel. The current plucked at him as he worked around the ship, hand over hand, looking for anything alien clamped or attached. Above in the light were vanishing bell-shapes of greeny-blue but down below, where the waters deepened from navy into black, there was nothing but nameless primeval fear. He hauled himself around, examining propellers and rudder, and then checked along the other side. His muscles were exhausted in the cold water.

Onshore, Bailey accepted Crabb as a member of the clearance diving team. Bailey and Leading Seaman Bell had been the first responders to the thwarted twelve-strong Italian frogman attack back in July. Bailey had dived to find limpets, live and primed, underneath the ships’ hulls. By knifing their pneumatic tubes he got the mines to drop to the sea bed where they could explode harmlessly later. Bailey won the George Medal for this, but soon after inducting Crabb into his trade, he tripped and broke his ankle. Now Lieutenant Crabb became the Diving Officer.

News came from a British agent at Huelva that a new kind of mine had washed ashore in Spain. It seemed to have a delayed-action fuse operated by a small propeller turned by motion through water. An enemy frogman could easily attach the mine below a ship’s waterline in a neutral Spanish port, but it was not designed to go off there and then. Only after the ship had travelled a certain distance away, and the propeller had made a certain number of revolutions, would it suddenly explode, making people think it was a torpedo or a sea mine. Now British ships arriving in Gibraltar all had to be checked underneath. A week after his first dive, on 4 December 1942, Crabb found a device on the 1200-ton steamer Willowdale, which was carrying a valuable cargo of tungsten or wolfram.

The green torpedo, about a metre long, was attached to the bilgekeel near the ship’s engine room by three clamps that Crabb had to undo. But did they turn clockwise or anti-clockwise? Was it ‘righty-tighty, lefty-loosey’ as normal, or the other way around? If you were wrong, would the attempt to unscrew it trigger a booby trap? Unexploded ordnance waiting to go off is frightening. It took Crabb forty-five minutes of effort underwater and three bottles of oxygen to loosen the clamps. He couldn’t bring the mine up or let it drop in case it had a hydrostatic pressure gauge that would explode it at a certain depth, so he tied it at the same depth to a buoy, which was towed by rowing boat to Gibraltar’s Rosia Bay. Crabb could not leave it there because it was a popular swimming spot. So, the next day, he rowed the buoy northwards and bravely carried the twenty-five-pound bomb ashore at the end of the airstrip, still packed with Spitfires after Torch. Without informing the RAF, he and Commander Hancock started dismantling it. The propeller mechanism was not the only way to explode the TNT, they found. Inside the casing were three time-clocks and three stubby detonators which Hancock went off to show to Admiral Edwards-Collins and General Mason-MacFarlane.

Crabb also inspected the improvised harbour defences against frogmen-swimmers and human torpedoes that ordinary nets and booms might not keep out. There were two entrances to the harbour, either north or south of the Detached Mole, and two crude mortars guarded each one. Necessity was still the mother of invention in Gibraltar, just as it had been in the Great Siege. These defensive mortars were essentially five-foot lengths of boiler pipe held upright in a wooden frame, with a Lee-Enfield .303 bolt-action rifle’s mechanism, trigger and butt welded into the bottom of the pipe. The mortar bombs were ordinary food tins, four and a half by three inches, filled with a pound and a half of TNT with a nitrocellulose fuse that would burn underwater.

The home-made mortar, or Modified Northover Projector as it was grandly called, was supposed to work in the following way, but didn’t always. First you loaded it, by putting a blank .303 cartridge into the rifle’s chamber, and then you slid a mortar bomb, made from a food tin full of TNT, fuse first down the barrel of the pipe so it sat snug above the cartridge. You fired the mortar by a sharp tug on the lanyard which pulled the trigger on the rifle. This drove the pin-striker into the cartridge’s percussion cap, whose explosion ignited the gunpowder packed next to it in the cartridge tube. The resulting jet of flame was supposed to light the fuse on the bomb and the expanding gases of the cartridge’s gunpowder would blast the now sparking can of TNT out of the pipe and high up into the air before the projectile splashed into the sea, sank, and finally exploded under the water. If the fuse did not light, then the bomb was a dud. If the tin can did not come out of the barrel, you were advised to get down behind a concrete wall in case the whole contraption blew apart. This was why you pulled a lanyard from a distance and ducked until you saw the spark on the tin in the air.

When it worked, a bomb exploding underwater was more dangerous than one exploding in the air. As those who fish with dynamite know, water transmits shockwaves horribly well. The radiating and bouncing pressure wave can pulverise soft tissue without breaking skin.

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Across the bay in Algeciras, on board the Olterra, twenty-seven-year-old Lieutenant Licio Visintini was getting ready for his big coup. He had been studying the mortars through his British binoculars – the shots were irregular but at roughly three-minute intervals, and he reckoned he could slip in between them. ‘Bursting bombs and darting patrol boats only strengthen our will to defy the enemy offensive,’ he wrote to his wife, Maria.

Visintini had three ‘hogs’ and six men ready and waiting for a good target – the return of Force H from Torch operations, led by the battleship Nelson, the aircraft carriers Furious and Formidable and the cruiser Renown. The fifth underwater attack on Gibraltar was to be his glorious moment. ‘We are going to sea,’ he pencilled on a sheet of paper to his wife for the last time, ‘and, whatever happens, we are determined to sell our skins at a very high price.’

The six men set off for Gibraltar harbour early on 8 December 1942 in Operation BG5. Deep down inside the Olterra, the two-ton ‘hogs’ were lowered on slings into the flooded compartment. Licio Visintini and his ‘oppo’ Sergeant Giovanni Magro put on their breathing gear and pushed the first ‘chariot’ out of the hatch cut in the forepeak. Manisco and Varini followed, and Cella and Leone brought up the rear.

Only Vittorio Cella of the six-man team made it safely back to base in Algeciras. Operation BG5 was a heroic but futile attack. What seems to have happened is that a rough and ready piece of kit, a tin of TNT lobbed from a bit of British drain-pipe, sank a fine piece of Italian engineering at the harbour mouth. Visintini and Magro were killed; Salvatore Leone drowned; Girolamo Manisco and Dino Varini scuttled their craft and were captured (they said they were off the submarine Ambra, to keep Olterra’s secret safe).

Crabb spent all night scouring ships’ hulls for explosives, which could have potentially killed him if he had come within a half-mile of their explosion, but found no 300 kg warheads had been clamped in place. Then he searched deeper for the two-ton scuttled ‘hogs’, without success. Two corpses were recovered from the harbour, their names, Visintini and Magro, still on their overalls. In the morgue, Crabb and Bailey saw what the TNT explosion had done to their bodies and their kit. This, then, was how divers came to grief, down in the depths. Crabb thought about dying underwater; this could be his own death. He was a Catholic, so he invited a priest to officiate on the tender as he and Bailey gave their enemies a respectful burial at sea, sliding them from under a couple of Italian flags, and then dropping a wreath on the waters. (Later, in 1945, while clearing German mines laid in the canals of Venice, Crabb would willingly give a secretarial job to Visintini’s widow, Maria.)

*

New recruits joined Gibraltar’s British Underwater Working Party, and they moved, together with the bomb-disposal men, into the strong-point of Jumper’s Bastion. There was a catch-phrase in the wartime radio comedy show ITMA that everyone listened to, ‘Don’t forget the diver, sir!’ and Admiral Edward-Collins did not, but raised their pay in Gibraltar. All ranks got an extra half-crown for every dive undertaken; both sides of a ship counted as two dives. Petty Officer Thorpe sorted out their oxygen booster pump and instituted regular changing of CO2-scrubbing granules so that the Davis Submerged Escape Apparatus (DSEA) kits worked efficiently. A seventeen-foot-deep training-tank was built using an old ship’s boiler, upended in Rosia Bay and warmed by salt water that had been cooling the distillery.

All ships had to be checked for mines, so they had plenty to do. A Spanish waterboat regularly brought fresh water for the garrison over from Algeciras, and the Italians thought it might be a good idea to tuck a manned torpedo underneath; but Crabb, alert to that possibility, checked the waterboat on every trip. Two British divers, Morgan and Knowles, went across to Algeciras on the waterboat disguised as crew and wandered over to where Olterra was moored. They strongly suspected that the ship was a frogman base, but because everything looked normal on the surface and they had no proof, higher authority forbade them from even making a secret inspection below the waterline in case it caused a diplomatic incident with Spain. According to Frank Goldsworthy, Crabb robustly suggested limpet-mining the Olterra at its mooring in Algeciras, but this was turned down at Cabinet level. Decima Flottiglia MAS was left with enough time in the summer of 1943 to achieve two more underwater attacks on Gibraltar and seriously damage six more ships.