He left the cabin and went to the wheelhouse. There was the noise of activity on deck and Prince could sense the trawler’s speed being cut. More activity in the wheelhouse: from what he could tell, Shaw was now in charge. ‘That’s them, it’s the right signal!’ he heard the young Royal Navy officer shout.

A few minutes later there was a knock on the cabin door and Sid Oliver popped his head round it. ‘Come on, Tom, it’s time now.’ He looked behind him and quickly thrust a small flask into Prince’s hands. ‘Rum: drink that and everything’ll be fine.’

When Prince reached the deck, Jack Shaw was coming down from the wheelhouse. He led him to where the deckhands were hanging tyres over the side of the trawler. Out of the darkness, a shape loomed into view. As it came closer, he could see it was a Danish trawler: Lena, Esbjerg.

The skippers of the two trawlers took five minutes to manoeuvre the boats alongside each other. The tyres ensured they came together smoothly, and then ropes were lashed at the bow and stern, held in place by deckhands on either vessel.

‘You’ve got everything?’ A wind had picked up and Shaw was shouting to be heard above it. Prince said he had, and with that, he was helped over the side of the Northern Hawk and then more or less hauled onto the wet deck of the Lena. Even before he’d clambered to his feet, the two trawlers had separated and the Northern Hawk was pulling fast away from the Danish boat. One of the Danish crew pointed to an open hatch. ‘Down there – quick.’

They arrived in Esbjerg a few hours later on the high tide. Prince was uncomfortable from being kept in the hold throughout the journey, and he reeked of fish. He was grateful for the rum Sid Oliver had given him. He waited below deck while the fish was unloaded. A period of silence followed, and he wondered if they’d forgotten about him. Then one of the crew came down, opened a door and led him into the engine room. Another pointed to a small hatch. ‘Go in there: just a few minutes. Not a sound.’

It was the shape and size of a coffin, the air limited and suffused with the smell of diesel and fish. Prince could hear people walking past and talking. He could make out that they were speaking Danish, although not what they were saying; he could also have sworn he heard some German. Half an hour later, the hatch door opened.

‘Out you come.’ It was a man in his sixties, distinguished-looking, with an irritated air about him. ‘I trust you had a successful trip. What fish did you catch?’

What fish did you catch? Prince knew he was safe. This was Niels, his contact in Esbjerg.

‘Only haddock, I am afraid.’