On a freezing morning in early 1942, Janet Okell arrived at Western Approaches HQ for her first day at work in a fluster. The nineteen-year-old1 Liverpudlian, who had lived her entire life less than ten miles from Derby House, on the banks of the River Dee in Park West, Heswall, didn’t know that she was supposed to have already collected her Wren uniform.
As she passed through the rasping, gas-blocking mesh curtains into the concrete-roofed bunker, Wrens in pristine shirts and ironed skirts looked her up and down. Not only was she improperly dressed, Okell–whose curly bobbed hair made her look as schoolgirlish as she felt–was lost in the building’s warren of cable-laden corridors. With a gathering sense of dismay, she wandered until a passing Marines corporal noticed her distress and took pity on her.
By the time Roberts arrived to collect her, Okell was in tears. She looked up into the gaunt but kindly face of her new boss, who handed her his handkerchief. She thanked him and blew her nose.
Roberts guided Okell–one of four young ratings who had been selected to support his crack team of officers in setting up the tactical school–to a heavy wooden door marked with the letters ‘WATU’. Between the ‘A’ and the ‘T’, there was a circular badge, inscribed with the word ‘Tactician’. At the centre of the badge was a miniature chessboard, showing a white king forlornly hemmed in by two black knights, castles and bishops, and below it the capitalised declaration ‘CHECKMATE’.
The badge had once belonged to HMS Tactician, a First World War destroyer that had been sold for scrap in the 1930s. The salvaged memento provided a daily reminder to every Wren and naval officer who passed through the door of the unit’s ultimate purpose: to win, through a combination of superior tactics and consummate gamesmanship, the Battle of the Atlantic.
Roberts opened the door for his new Wren, and asked her to follow him past the newly refurbished offices and rooms, which included a lecture theatre that could seat fifty, into the main, expansive room at the heart of the school. All evidence of bomb damage had been scrubbed away, and the room now resembled something between a school gymnasium and, thanks to the scattered sticks of chalk and tumbles of string, a child’s playroom. The floor in the centre of the room was covered in brown linoleum, painted with white gridlines and punctuated with tiny wooden models, some of which had been fashioned from wood taken from HMS Nelson, an armoured cruiser built in the 1870s that had been scrapped in 1910.2
As Okell surveyed the floor, Roberts explained that each white line was spaced ten inches apart, representing one nautical mile, while the counters represented ships and surfaced German U-boats.
‘Think of it like a giant chessboard,’ he said.3
Like Alice Through the Looking Glass, Okell had stepped into a board game. The map, Roberts explained, represented the Atlantic Ocean. Okell would help stage recent sea battles. The ‘board’ was large enough to accommodate twenty-four players at a time. In trousers and white shirts, with their sleeves rolled up, the Wrens would kneel and carefully move the pieces according to the players’ orders.
Around the edges of the room, Okell noticed great sheets of white canvas. They were arranged into enclosures, like voting booths, except each one seemed to have a peephole cut into it at eye level. The average visibility from the bridge of a warship is five miles, Roberts explained. The canvas sheets were positioned in such a way that, when a player peeked through the slit, he or she could see the equivalent of a five-mile view of the tiny wooden ships on the floor. Linen side wires, which could be bent to adjust visibility, depending on the game scenario that was being played, held the apertures open.
‘Like this,’ said Liz Drake, a Wren officer who at just five feet two needed a six-inch stool, especially made for her, to reach the slits.4 Drake disappeared behind the canvas and, a few seconds later, Okell saw the flap roll back and her colleague’s eyes appear, blinking, in the hole. For Okell, a bridge player who had joined the Wrens from secretarial college expecting to be assigned as a typist, it was a curious scene. Roberts, with his teacherly flair, began to explain the rules of the game, recently formulated, broadly untested.
One team, positioned behind the canvas sheets at desks, played as the escort captains, he said. The other, usually captained by Roberts or his right-hand woman, Jean Laidlaw, played as the U-boats. As in the real Battle of the Atlantic, each side’s objective was focused on the convoy ships: the escort ships had to protect them, while the U-boats had to attack them. Each side had a secondary objective. For the escort ships, this was to sink as many U-boats as possible, while the U-boats hoped to avoid detection and exit the battlefield unharmed.
The convoy ships, the prize in play for both sides, would automatically plod on at each turn of the game toward their destination, the battle raging around them, just as at sea. Next, Roberts explained the rules of the game. Players were given two minutes in which to submit their orders for the next ‘turn’, to replicate the urgency of a real battlefield. The movements of the U-boats were drawn in green5 chalk on the floor, a colour chosen as it was impossible to make out against the floor’s tint when viewed from an angle. This ensured the U-boat positions were undetectable to the players peering through the canvas screens. The escort ships’ movements would then be added to the floor in white chalk, which was, in contrast to the green markings, legible to those peeking from the canvas holes. Turn by turn the pieces would move around the floor, as the escort ships dashed to the site of an explosion to drop depth charges, and the U-boats performed their feints and dodges in an effort to pick off convoy ships, while evading the escort.
Okell’s role, Roberts explained, would be that of an umpire, measuring distances and marking movements in chalk to ensure that the game played out as accurately as possible. Finally, at the end of the game, the players would come together and, sitting around the board, now criss-crossed with chalk markings, Roberts would reveal how everyone had fared. More details needed to be worked out, Roberts explained, and by necessity the game was a simplification of real U-boat action, but there was enough here, he said, to begin staging recent sea battles. The objective was to experience the action from the perspective of the U-boats and, from that knowledge, assess what the escort commanders might have done differently to save ships, supplies and lives.
The tour complete, Okell was told to fetch her uniform and, like every other Wren who joined WATU, report to the basement. There she would be trained as a plotter;6 after all, the skills required to measure out distances on the giant map in Derby House’s basement were precisely those required to play and direct the game. Okell left Derby House and made her way to the uniform store, situated in the nearby Liver Building7, understanding the responsibility that she now shared.
With the rudiments of the game in place, Roberts spent a great deal of his time studying after-action reports written by naval officers who had battled U-boats and survived, in search of clues to their tactics. Being ideally situated to meet and quiz any and every naval officer passing through Western Approaches Command, Roberts did not have to rely solely on the rather staid written testimony of sailors; he could also listen to first-hand accounts by interviewing men as they returned from sea.
During the course of several interviews a chaotic picture emerged, not only of the sea battles themselves but also of the training process. Before deployment every sailor–an estimated 200,000 men by the end of the war8–underwent a two-week crash course in Tobermory harbour, on the Isle of Mull, under the gruelling tutelage of Sir Gilbert Stephenson (nicknamed, variously, ‘Puggy’, ‘Monkey’ and ‘The Terror’). Stephenson’s course was intended to build and improve efficiency among an individual ship’s crew, but it did not address the effectiveness of ships working in company. Not only was there no universal set of tactics with which to fight U-boats, neither was there any training for how escort ships should work as a team. The destroyers and corvettes, it seemed to Roberts, were broadly free to direct their response according to individual whim or notion.
Fred Osborne, Nancy Osborne’s brother and first lieutenant of the corvette HMS Gentian, who like his sister came to Britain from Australia to join the war effort, described convoy defence as ‘difficult and haphazard’ in the absence of collective countermeasures.9 ‘No clear doctrine for combatting attacks on convoys had been formulated and taught,’ he later wrote. As such, ‘the losses were appalling’.
Roberts asked every escort captain he interviewed the same question: ‘What do you do when a ship is torpedoed?’ Some spoke of ‘going to action stations’, others about increasing their speed. When pressed, however, most shrugged in resignation. What could you do, blind in the night, explosions sounding all around, when your ASDIC operator was unable to distinguish the sound of a U-boat cleaving the water from the noise of a choppy sea, or even a shoal of fish?10
One man, however, had a different answer. Grizzled and terse, Captain Frederick John Walker, known as ‘Johnnie’ to his men, after the whisky, inspired loyalty from his crew that ran even deeper, in many cases, than their sense of duty to country. Even by 1942, after just three months captaining a ship in the Atlantic, Walker had become one of the only successful U-boat hunters in the navy.
On his first voyage as commander in December 1941, only a few weeks before Roberts and Walker met, Walker had sunk two U-boats, and led the escort ships under his command in the sinking of three more. While an Allied escort carrier and two convoy ships had been lost in this battle for convoy HG.76, it was nevertheless considered by many to be the first major victory of the war for the escort ships against the U-boats. How had it been done, Roberts asked?
Walker believed it was down to a tactic that he had developed and dubbed ‘Buttercup’, a nickname he used for his wife, Eileen. Before Walker docked on his return journey from the battle, he had received a message from Sir Percy Noble requesting a meeting. There he was asked to explain the secret to his success. Desperate for something on which to pin their tactical hopes, Noble and Walker’s superiors seized on Buttercup. Walker was commanded to write up the manoeuvre, which was to be sent to escort commanders for immediate adoption at sea.
There was just one problem: ‘Buttercup’ was utterly ineffective and, unknown to Walker, Roberts had been secretly asked to expose it as such.
Captain Walker’s interest in anti-U-boat tactics long pre-dated the war. In the 1920s, years before he was made a captain, Buttercup’s inventor had volunteered to undergo a course at HMS Osprey, the school of anti-submarine warfare at Portland naval base. Never reticent to criticise instructions that he considered to be ill conceived, Walker’s outspokenness earned him the respect of his contemporaries, and the misgivings of his superiors, who viewed his unmoderated candour as a character flaw.
When Walker was appointed to second-in-command of the battleship Valiant, he regularly clashed with his captain; a confidential Admiralty report described Walker as ‘lacking powers of leadership’. Resigned to the belief that he would not make captain, Walker returned to Osprey as commander in 1937. In the navy there was a small window in which every officer could be promoted to the next rank of seniority. Those who failed to earn promotion within the designated time frame were known as ‘passed over’. In peacetime, an officer who had been passed over could elect either to remain in the service at their existing rank till retirement age, or retire early with a modest pension and the opportunity to pursue a civilian career. Walker considered leaving the navy while he still had time to follow a new calling. As war approached, however, along with scores of other officers who had also been passed over, Walker was called upon to fill positions of importance.
Walker had long maintained that U-boats would become the principal threat to Britain’s survival. In his new posting he was given an office in Dover Castle and tasked with overseeing anti-submarine defences in the Channel, specifically the laying of extensive, underwater minefields designed to frustrate any German attempt to invade England from France. For Walker, who desperately wanted a ship to command, it was a disappointing appointment. As the months passed, Walker bombarded the Admiralty with requests to transfer to a ship. Each letter was met with another refusal. Finally, in March 1941, Walker travelled to London to meet Captain Creasy, director of anti-submarine warfare and an old friend, to make his request in person. Creasy was one of those few officers who knew the truth about Allied losses in the Atlantic, and the extent to which official statements about U-boat sinkings had been exaggerated. As such, he was keenly aware of the need for officers with experience of fighting U-boats to join the team at the newly formed Western Approaches HQ in Liverpool.
Walker may not have had this exact kind of hands-on experience, but his knowledge of tactical theory was expansive. Creasy listened to his friend’s arguments about why he should be given command of an escort ship and, at the end of the meeting, offered Walker an assurance that he would request a transfer. Six months later a signal arrived at Dover from the Admiralty ordering Walker to Liverpool. He was to assume command of HMS Stork for duties in the Atlantic. On arrival Walker found himself among ‘strangely assorted bedfellows’, as his biographer put it.11 So it was that Walker and Roberts, two of the navy’s most precocious and single-minded misfits, came to meet.
The men took an instant dislike to each other. Walker, who was four years Roberts’ senior and looked a good deal older, was taciturn. Roberts was effusive. Walker shunned the limelight (as a child he had performed in a ballet at the Royal Albert Hall, only to burst into tears on stage, an indignity that his elder sister claimed had contributed to his refusal to be the centre of attention12) while Roberts, who still felt the pain of his dismissal from the navy, was determined to fight for recognition.
‘Their personalities were diametrically opposed,’ wrote Fred Osborne, who would later spend eight months working alongside Roberts.13 Then there was the rivalrous symmetry of their missions. Like Roberts, for years Walker’s understanding of U-boat warfare had been purely theoretical. But after three months working out of Liverpool, Walker had the advantage of live encounters with U-boats. The ‘notorious disagreements’, as Fred Osborne put it, between the two men became common knowledge at Derby House and, despite repeated orders from his superiors, Walker resolutely refused to visit WATU, choosing instead to potter in his garden at home, or take his wife and child on shopping trips.14
Nevertheless, this first meeting between the men had been cordial and, for Roberts, useful. Before he had left for Liverpool at the beginning of January 1942, Admiral Usborne, Churchill’s aide, had told Roberts that he privately doubted the efficacy of Walker’s lauded ‘Buttercup’. Usborne suspected that Walker’s sinking of U-boats in December was not by design but ‘by luck,’ as he put it to Roberts, and that Buttercup had been wrongly feted for the success.15
When Usborne had raised his misgivings with Captain Creasy he had been told to ‘mind his own business’. Irritated by this rude brush-off, Usborne asked Roberts, as one of his first tasks at WATU, to analyse the battle of HG.76, where Walker had seen such great success, in order to settle the matter one way or the other.
Oblivious to Roberts’ ulterior motives, Walker outlined the tactic. On the order ‘Buttercup’, he explained, all of the escort ships would turn outward from the convoy. They would accelerate to full speed, while letting loose star shells–an explosive that, like a dandelion puffball, released iridescent fragments that hung in the air on a parachute for up to sixty seconds and illuminated the ocean. If a U-boat was sighted, Walker would then mount a dogged pursuit, often ordering up to six of the nine ships in his group to stay with the vessel until it was destroyed.
Walker’s absolute belief in the tactic is clear in the operational instructions he wrote for the captains within his group.
‘I cannot emphasise too strongly that a U-boat sighted or otherwise detected is immediately to be attacked continuously… until she has been destroyed, or until further orders have been received,’ he stated.16
Coordination and cooperation, Walker explained, were key to success. He viewed the escort group as a kind of sports team, and himself, as commander, in the role of player-manager.
‘This kind of warfare is not the sort that has one man as its ace protagonist,’ he later said during a speech delivered at a ceremony in Liverpool to commemorate his success in the U-boat war. The mayor presiding over the ceremony had described Walker as the navy’s ‘number one U-boat killer’, an accolade the captain immediately shrugged off. ‘Fighting U-boats is very much like playing football, or any other sort of game,’ he continued. ‘You have a team of a thousand men, any one of whom can wreck the whole show if he doesn’t do his job properly. Every man has his job to do. I am merely at the head of the affair.’17
Roberts left the meeting armed with everything he needed to restage the battle of HG.76 in the game and thereby test Buttercup’s worth. Despite his misgivings about Walker’s tactic, he could not deny the truth of his rival’s assertion that escort ships should work not autonomously, but as a coordinated team. Regardless of Buttercup’s validity, Walker’s promotion of teamwork between escort ships was surely key.
Upstairs Roberts and the Wrens laid out a plot of convoy HG.76 on the floor, including tokens to represent not only Walker’s 36th escort group, but also the destroyers Blankney, Stanley and Exmoor, and the convoy aircraft carrier HMS Audacity,* which had loaned their support to the convoy on its homebound journey from Gibraltar. In all, the pair arranged forty-eight ships in twelve columns.18 Then, the two men added the tracks of the three U-boats known to have participated in the battle, U-434, U-574 and U-131.
The stage set, Roberts began to move the convoy, which spread across six white lines on the floor to represent its six-mile width, in two-minute intervals and at a simulated rate of ten knots. Each move was made in precisely the same pattern as Walker had directed the actual escort a few weeks earlier.
Blow by blow, Roberts imitated the action, as per the official reports. He replayed the moment that one of Audacity’s aircraft sighted a shadowing U-boat. He peeled Walker’s HMS Stork away from the rest of the escort ships and placed the sloop in active pursuit of the U-boat, dropping a barrage of imaginary depth charges on U-131 and then, when it surfaced two ‘hours’ later, sinking it with a spray of gunfire. (Doenitz, who had also watched the encounter play out on his plot, albeit almost in real time, realised that Audacity’s scout planes had led to U-131’s downfall, and issued orders that in the event of sighting an aircraft carrier in any convoy, every wolfpack was to prioritise attacks on this ship above all others.19)
Seeing the battle from a crow’s-nest perspective above the board, it became clear to Roberts that this early success in the battle had been a direct result of the unusually large number of escort ships that Walker had at his disposal. This had freed him to pursue the spotted U-boat while leaving the convoy ships with adequate protection.
What was less clear to Roberts was precisely what had happened next. After successfully destroying another U-boat three days later, the first merchant ship, Annavore, was torpedoed and, at 11 p.m. on 21st December, so was HMS Audacity, whose captain had ignored Walker’s orders and had taken up position on the unprotected starboard side of the convoy.
Roberts placed a tiny flag in two of the ship models, to indicate that they had been removed from the game.20 Then, as he examined the plot, a question formed in Roberts’ mind. If the U-boats were firing from outside the perimeter of the convoy, how had Annavore, which was in the centre of the convoy, been sunk? Might it be possible, he wondered, that the U-boat had attacked the ship from inside the columns of the convoy? There was, he reasoned, a simple way to prove his theory.
‘Hold everything,’ Roberts told his staff, as he rushed into his office to make a phone call.
Roberts picked up the receiver and asked the operator to put him through to the Flag Officer Submarines in London, hoping to speak to its chief of staff, an old friend, Captain Ian Macintyre.* To Roberts’ astonishment, the flag officer himself, Admiral Sir Max Horton, picked up.
Horton, known by reputation to Roberts, was a man of foreboding distinction. As a young submarine commander in the First World War, Horton had become known as an unparalleled terroriser of German ships, and he had sunk the first enemy ship of the Great War. On return to port, Horton would signal a successful kill by flying the Jolly Roger, a tradition that continued till the end of the Falklands War. Horton’s precocious talent as a submariner propelled him up the ranks; years later his biographer would describe the admiral as ‘the greatest authority on submarine warfare’.
On the phone, Roberts explained who he was and asked Horton if he might be permitted to ask a question. During the last war, Roberts asked, would you ever have crept among the ships of a convoy to fire a torpedo?
‘Of course,’ replied Horton. ‘It is the only way of pressing home an attack.’
And out of interest, Roberts continued, what is the range of a U-boat’s electric torpedo?
‘Five thousand four hundred yards,’ replied Horton without hesitation.
‘Thank you, sir,’ said Roberts, before he hung up.
‘This was enough for me,’ he wrote in his diary.
It was late, but Roberts asked Laidlaw and Okell if they might stay behind with him to reset the plot and run a new game on the giant board. The two women, infused with Roberts’ excitement, agreed and hurriedly reset the game. This time, Roberts placed a U-boat model in the centre of the columns of the convoy and ran the events of Walker’s battle in reverse. If the range of its torpedoes was around two and a half miles, it was reasonable to imagine that U-boat captains would fire from less than half that distance, in order to maximise their chances of scoring a direct hit.
Between them, Roberts and the two Wrens began to plot different scenarios that might have enabled the U-boat to sneak into the convoy without being detected. Only one checked out: the U-boat had entered the columns of the convoy from behind. And it must have done so on the surface, where it was able to travel at a faster speed than the ships. By approaching from astern, where the lookouts rarely checked, the U-boat would be able to slip inside the convoy undetected, fire at close range, then submerge in order to get away.
If this was all true, Roberts surmised that Walker’s depth charge, dropped after spreading out from and not into the convoy, must have hit not the attacking U-boat, but another loitering member of the pack. If so, Usborne was correct: Buttercup’s success was by fluke, not design.
Roberts and the Wrens headed to the kitchen to make coffee and a round of corned beef sandwiches. The conversation continued to centre on the battle they had left on the floor of the game room. The group discussed how if they were a U-boat captain having made a point-blank-range attack on a merchant ship, they might attempt to escape unharmed. The game had enabled the fledgling tacticians to think like U-boat captains, and from that perspective the answer suddenly seemed obvious: having made your attack, you would of course dive. Then you would sit and wait for the convoy to roll overhead.
‘Eventually,’ Roberts concluded, ‘I would emerge, deep, from the stern of the convoy.’21
With the U-boat tactic abruptly unveiled, Roberts wanted to try out some potential countermeasures that might foil the plan. The four returned to the game room. Roberts assumed the role of the U-boat captain, and Laidlaw and Okell played as Walker’s escort ships. The countermeasure revealed itself immediately. Rather than splay out from the convoy at speed, dropping depth charges at random, Laidlaw and Okell lined the escort ships up around the convoy. While the convoy continued on its way, each escort ship performed a triangular sweep, listening for U-boats on the ASDIC.
With a mounting sense of excitement, the team ran the procedure twice more. In both instances Roberts’ U-boat was detected and sunk. It was, by now, the early hours of the morning; in all the excitement time had passed unnoticed. Roberts ordered a staff car to return the two women to Ackerleigh House.
The next morning, Roberts and the Wrens reassembled in WATU’s game room and began replaying the battle, and their new counter-tactic, again and again.*
‘I couldn’t pick a hole in it anywhere,’ Roberts wrote in his diary.22 He formulated the counter-attack as a set of operational instructions and, when he felt ready, Roberts left a message with the duty officer that he would like to see Sir Percy Noble as early as possible. He had something to show him.
The next day Noble, flanked by his staff, entered the game room. The commander-in-chief warily eyed the chalk markings on the floor, and the canvas sheets decked out like ship portholes. What was all this make-believe nonsense? Undeterred, Roberts began to explain their discoveries–how the U-boats would slip between the convoy ships on the surface of the water, at night, when they were unlikely to be spotted, make their attacks, and then dive to wait until danger had passed.
The atmosphere was frosty. Noble had made no secret of his condescending scepticism towards WATU’s work. Roberts detected the same tone in Noble’s manner–‘snootiness’, as he described it in his diary–that he had perceived during their first meeting. How could this former naval officer, with his nubs of chalk and jumbles of string, contribute anything to the battles being waged out at sea? Games, Roberts knew, were seen as frivolous things supposed to be set down in adolescence and not taken up again until retirement. They had no place in the adult world, let alone the dread theatre of war.
When Roberts explained that he had spoken to Sir Max Horton, the submarine ace, and as the escort team’s counter-attack showed its effectiveness on the game floor, Noble’s demeanour appeared to change. Sensing the shift in atmosphere, Roberts quickly asked Laidlaw to assume the role of the U-boat commander and Okell that of Captain Walker. Then, as the two women played out the battle, Roberts began to demonstrate WATU’s findings. When Laidlaw fired a torpedo from within the convoy’s columns, then dived, Roberts commanded Okell to perform the team’s newly developed counter-tactic, by moving the escort ships in their triangular sweeping patterns designed to flush out the hidden U-boat. While performing the sweeps, one of Okell’s escort ships picked up the Germans’ position on its radar.
As the demonstration unfolded Noble and his staff seemed ‘to sit forward on their chairs’. With the U-boat position revealed, Okell dropped a cascade of depth charges over its position beneath the water. There was no time for Laidlaw to manoeuvre her U-boat out of the way. Okell scored a direct hit, and the U-boat ‘bubbled’ to the surface. The demonstration at an end, Laidlaw rose, and Okell emerged from behind the canvas sheet, from where she had been directing the escort ships. Roberts looked at Noble, in the judgement seat.
‘Congratulations,’ said Noble. Then, the commander-in-chief of Western Approaches turned to one of his men and told him to take down a message, to be sent post-haste to the prime minister.
‘The first investigations have shown a cardinal error in anti-U-boat tactics,’ he said. ‘A new, immediate and concerted counter-attack will be signalled to the fleet within twenty-four hours.’23
An air of friendship, Roberts noted, had arrived in the room. Noble now asked for a name for the tactic from the inventor. Roberts explained that Jean Laidlaw, who had ‘done all the boring statistics’, had christened it Raspberry. The manoeuvre was, she had reasoned, a razz of contempt aimed at Hitler and his U-boats.
Noble chuckled, stood and made to leave. In the doorway he paused, turned and strode up to Roberts.
‘Sew on your fourth stripe,’ he said. The retired commander was now a captain.
For many days thereafter, visitors came to WATU to see the game for themselves. The team would first demonstrate Walker’s tactic, Buttercup, in order to reveal ‘its fallacy’, as Roberts put it. Having issued this two-finger salute to his celebrated rival, Roberts then oversaw the triumphant performance of his superior manoeuvre, Raspberry.
‘It made me rather unpopular with Captain Walker,’ he wrote.