Full surprise was achieved with the mines, which were blown at ten-second intervals, with the artillery only opening fire on the detonation of the first pair. The troops were warned to take cover from the debris, which was thrown 200–300ft high and scattered over 250yds, although a man who looked over the parapet to see the explosions was killed. Those Germans who survived the mines were overwhelmed by the attackers, who took the craters in minutes, and the actual assault cost the British just seven casualties, although the Germans brought very heavy fire onto the captured positions.⁶

It was realized that Hill 60 alone would be difficult to hold, as the Germans were still in possession of the Caterpillar on the opposite side of the railway cutting. Two days after the capture, Norton Griffiths visited Major William Johnston VC, commanding 172 Tunnelling Company, which had just taken over the Hill 60 sector. Norton Griffiths was constantly looking for opportunities for his Moles and recommended that General Glubb should now attack the Caterpillar:

It is important for the Chief Engineer to know that some 450 feet from the position we now hold there is another Hill which is strongly fortified. It would be easy to mine this from the position we now hold running the Mole along the side of this Hill & then run under them. A good blow & happy results could be obtained here. Johnston keen on this & no time should be lost to get busy at once.⁷

Norton Griffiths was also becoming aware of the larger potential of mining and the danger of using it merely to deal with positions which were a local annoyance. An officer on Glubb’s staff later described the problem of attempting to hold Hill 60 in isolation:

Probably, as events turned out, it would have been wiser to have raided the defences and retired as originally proposed, forcing the enemy to keep a large garrison on the hill exposed to fire if he wished to retain it. For Hill 60 when recaptured would form a small but pronounced salient, exposed to attack on both sides: officers who knew the ground were of [the] opinion that it could not be held unless the Caterpillar also was taken. (Col. James Edmonds, Staff Officer to Engineer in Chief, GHQ)⁸

Indeed, the Germans retook Hill 60 using chlorine gas just nineteen days later on 5 May and held it for almost two years.

The mine blows of 17 April apparently came as a surprise to the Germans⁹ and the difficulty of pushing forward tunnels at Hill 60 led to an attempt by the Experimental Company of the Prussian Guard Pioneers to use an electric tunnelling machine, without success (see Chapter 8). In early October the company was ordered to the sector on either side of the Menin Road to take over mine workings there, including at Hooge. The company took over the Divisional Mining unit and addressed the technical problem of sinking mines in this area, which led to successful blows in June 1916.

On 14 March the Bavarians fired two mines at St Eloi, south of Ypres, capturing the village, trenches including a mine shaft and a 30ft high heap of earth called the Mound by the British and the Lehmhugel by the Germans. After severe fighting the British retook the village, but the Mound remained in German hands.¹⁰

British mining was carried out by a Field Company, which ran out two galleries and was relieved on 25 March by 172 Tunnelling Company. Both sides frequently blew small charges against one another and then, exactly a month after taking the Mound, the Germans again fired a mine, creating a very large crater 70ft in diameter. It did not, however, damage a 172 Company shaft sunk from the cellar of a ruined house 50ft away.¹¹ The regular Sapper OC of 172 Company, Johnston VC, disliked mining and obtained a posting in early May, leaving in command a Territorial Captain in the Monmouthshire Regiment, William Clay Hepburn. Hepburn was an experienced mining engineer and colliery agent and the first non-regular Sapper to command a Tunnelling Company.¹² Norton Griffiths worked to persuade GHQ that mining engineers should be allowed to command Tunnelling Companies and by the autumn of 1915 this became accepted.

Hepburn placed Lieutenant Hickling in charge at St Eloi and by early July he and Second Lieutenant Gard’ner had charged two large mines of 1,400 and 1,500lbs and a series of smaller charges. The explosive was ammonal, a commercial blasting explosive safer and more powerful than gunpowder, which was to become the standard British mining explosive. Both of the two large charges were just short of the German front line and when blown would damage the parapets and bury the Germans with debris. Hepburn recalled forty-five years afterwards that he had gone to General Glubb, Chief Engineer of the 2nd Army, to ask for artillery support, but was told that there was insufficient ammunition for an attack and that he would have to blow the mines without an accompanying attempt to seize the craters. They blew the charges on 10 July: Hickling fired the right-hand charges and Gard’ner the left, which he described in a letter two days later: