For a while neither man said anything. The sea was calm and the same colour as the sky; impossible to tell where one ended and the other began. The gentle swell gave the impression that they were in the middle of an enormous shifting field, with the suggestion of hills rising far in the distance.

‘First time at sea, Tom?’

‘I guess it is really, yes.’

More silence. The skipper peered through the window to his right and then checked his dials. ‘We’re making good progress. We’re above Dogger Bank, you know. Wonderful fishing ground. They say that thousands of years ago this was all land, connecting Britain to the Continent – all the way from Lincolnshire to Jutland! You wouldn’t have needed us then, would you? Mind you…’ Another long pause; it seemed as if the skipper had lost his train of thought. ‘If we were still connected by land, the war would’ve been over long before now.’

‘Maybe it would never have started.’

‘Who knows.’

‘Were you in the convoys, Bert?’

The other man nodded.

‘And were they as bad as they say?’

‘Worse, far worse. We’ve lost dozens and dozens of men.’

‘You must have known some of them.’

The skipper nodded, staring hard ahead of him, his hands gripping the wheel. ‘My brother and brother-in-law.’

‘I’m sorry, Bert.’

Another long spell of silence. When Trent spoke again, his voice was barely audible above the hum of the engine and the crashing of the waves against the trawler. ‘And my son.’

Prince stepped to the rear of the wheelhouse. The thought of his own son overwhelmed him. He could feel the tears welling in his eyes, and all the time the Northern Hawk was taking him further away from Henry.

Late on Thursday afternoon, the Northern Hawk changed course and headed south from Dogger into German Bight, closer now to Denmark. The wind was against them and they’d increased their speed to eight knots, but the first mate thought he might have seen a periscope in the distance, and there was certainly a ship on the horizon, so they dropped their speed and cast their nets for an hour in case anyone was watching.

At eleven o’clock that night, Shaw called Prince into the cabin. A final check, he said. They went through the rucksack Prince would be carrying to make sure there was nothing that could link him with Britain, and then his papers to confirm they were all in order. Then Shaw quizzed him on the details of his new identity – where Jesper Holm was born, his date of birth. Finally Prince prepared for the rendezvous, wrapping his rucksack in an oilskin and putting on a lifejacket.

‘Wait here,’ said Shaw. ‘It could be any time now.’