The first planes appeared from the north just after midnight. Once the alarm sounded, he left the toilet block and ran into the woods, where he climbed a tree to get a better view.

He had no idea how many planes there were, but it must have been hundreds. At first there hardly seemed to be any bombs, but the area to the north of them was illuminated by hundreds of lights.

The second wave of bombers came around twenty past midnight. This time the target was further to the north, possibly the V-2 works. As soon as this attack finished, a third wave appeared, bombing targets even further north, maybe the experimental area. The anti-aircraft fire was in full operation now, and Prince spotted at least a dozen aircraft being hit.

Now the Trassenheide camp itself seemed to be the target, and he was terrified that stray bombs could land in the woods, so he jumped down from the tree and ran into the fields beyond, making sure not to get too close to the barbed-wire perimeter. As far as he could tell, the camp was ablaze.

The RAF bombers had been flying low, and as the final wave left, they seemed to descend before their final turn out towards the west, giving him a much clearer view. They appeared to be mostly Lancasters, and he was overcome by emotion. They’d have flown here from the bases in Lincolnshire he knew so well: Scampton, Wickenby, Woodhall Spa and Binbrook.

Just the year before, there’d been the thousand-bomber raids over Germany, and the planes had gathered in the skies above Lincolnshire before forming and heading out across the sea. They’d made so much noise that Henry had woken up, and father and son had stood in front of the blackout curtains watching them, Henry trying to count them.

Would Henry have been watching these aircraft as they’d left their bases earlier that evening? Would he see these same planes when they returned in a few hours’ time? And would he still try to count them?

His memory of the next twelve hours was a mixture of brutal clarity and blurred confusion. His main problem, as he looked back on it, was to recreate in his mind the correct sequence of events.

He remembered running from the woods towards the perimeter wire fence and then hearing a guard shout and running back to the huts. His own hut had taken a direct hit, as had the ones on either side of it. All three were so well ablaze it was impossible that anyone in them could have survived. A hut housing Ukrainians had also been hit, but there were some survivors there, all badly burnt.