I wondered what it looked like now. The DUK might have rebuilt them – not, I hoped, as concrete blocks, like on our side. And it was strange to think that, as I had walked up the eastern pavement of Regent Street just the previous day, past the empty windows of the big old stores, the buildings on the other side of the Wall had once looked out on to the same road, with gleaming displays of plush furniture, jackets and boots, cots. Those frontages had since been sealed in by the concrete border that had been built right up against them, and the buildings had been turned around to face the other way as if the division between us was just too grotesque to look at.

‘All this change,’ Tibbot said. ‘Do you even remember when the money had the King on it?’ Until he brought it up, I actually had forgotten that there had been a time when Marx and Engels had been absent from those little tokens. ‘Or all the other newspapers we had. Sunday Pictorial. The Times. Yeah, I bet you don’t even know how much you’ve forgotten.’

It was only a few minutes’ walk to Blackfriars, where we caught a fast train to Gravesend. Within an hour we stood in front of 2 King Henry Road – or what was left of it. Most of the street, it turned out, had been demolished to make way for a new block of flats. There were cranes lifting big concrete slabs into place, guided by men in helmets.

‘Lots of air raids around here just before D-Day,’ Tibbot said, looking at the rubble. ‘Going for the docks; and RAF Gravesend was a fighter airfield, part of Biggin Hill. These houses would’ve been hit a few times.’ On the train down, we had seen Yak fighters taking off on routine patrol – a strange twist of history, really.

‘You weren’t in the War, though, were you?’

‘Me? No, not this one. Far too old.’ The first War, I guessed. A pals’ battalion. Wipers or Gallipoli. Young men happily tramping off to what they had thought would be an adventure but finding only mud and drowning trenches. ‘Mate of mine at the station was RAF down here, though. He says it was chaos – the Stukas spent months busting up all our fighters on the ground. That’s why there was no air support on D-Day and the Luftwaffe had a free hand to bomb our boys on the way over. I’m glad I didn’t have a son.’

The road faced on to the Thames Estuary but was cut off from the water by the familiar steel fence and watch towers.