‘Keep her down, man. Don’t let her break surface. Down with her,’ said Raymond sharply.

The coxswains worked frantically and took her down to twenty feet. Then up once more and the periscope raised a mere few inches.

‘Bearing 175 deg. Full fields. Stand by!’ shouted Raymond, and down came the periscope again.

The motors eased down as the fields were increased by the torpedo ratings working at the motor-boards in the after compartment. Boyd dropped his notebook and stood by the firing gear.

‘Deflection’s twenty, sir,’ he said.

‘Open “stand by” valves,’ cried Seagrave. ‘Open the cocks on the firing line.’ A minute’s quick glance round, then ‘ready, sir.’

The periscope went up a few inches. Raymond was bending down almost on his back now in his efforts to show above water as little of his ‘look-stick’ as possible.

‘Port ten,’ he ordered. ‘Keep her at her depth. Steady the helm. Starboard five. Steady again.... Fire!’

Boyd wrenched down the firing levers, and the boat shuddered through all her frames as the torpedoes were hauled forward. There was a great soughing of air as the firing tanks recharged, the coxswains spun their wheels to counteract the loss of weight, and down came the periscope.

‘Eighty feet,’ said Raymond, rubbing his eyes.