Coming from Kent, I had never really known the devastation that London had suffered until one night when Nick and I had climbed up on to the roof of a theatre on Shaftesbury Avenue, home to all the grandest playhouses. He had pressed a coin into the hand of an usherette during the interval of a musical, and she had surreptitiously pulled aside the chain that closed off the topmost flight of stairs.

‘You see how some of these theatres have the roof missing?’ Nick had asked me as the cool night air drifted about us.

‘Yes,’ I replied. ‘The Blitz?’

‘Not quite. This street’s where the Home Guard made their last stand against the Nazis.’ He shook his head. ‘Old men up here with rifles and paraffin bombs against Panzers. Well, until the Luftwaffe blasted it all to bits. Poor blokes.’ I tried to take it in, but it wasn’t so easy. The official line that we were fed by the new state was that Churchill, in an act of supreme cowardice, had immediately signed the order of capitulation and saved his own skin by running off to Northern Ireland with the Royal Family. Others argued – discreetly – that he had been right to leave because someone needed to be in charge to direct the resistance, which was true. Well, you took your pick of viewpoints.

A night fighter on patrol passed overhead. Nick went right to the edge and peered down. ‘Have you taken out life insurance?’ I asked casually.

‘Sorry, old girl, not a penny. So there’s really no point doing it.’

‘Pity.’

We looked to the other side of the Wall. Cars buzzed about with bright headlamps; there were omnibuses full of people; and bustling shops, despite the late hour. Sometimes, if you were close to the Wall and the wind was right, you could hear music coming over – that very fast, jumpy American jazz with guitars and singers that they played occasionally on Radio Free Europe. Young people – the Teddy Boys especially – would head to the basement milk bars of Soho to try to guess how the dances went, re-creating the steps while they drummed on the tables with cutlery and fists. I had pictured Nick and myself over there dancing to the hot tempo music before laughing out into the street as the sun came up.

The train wheels crunched over tracks as Tibbot and I trundled back to London now. I looked out the window at houses passing in the night.

‘He’s lost,’ Tibbot said. And he waited for it to sink in. ‘I’m sorry, really, but if you keep on, it will only bring this down on you too. If they thought you knew anything about it, you would already be in one of their cells.’ He was right. By delving into Nick’s secret, I had made myself a target. And I had made Tibbot one too.