Knox’s bus quickly filled up with people who had stayed too late at work or given up the idea of walking home after an evening in a pub. The windows on the lower level began to steam up thanks to all the warm, breathing bodies and Knox was forced to abandon his rear-facing seat next to a man who had definitely spent the evening hunched over a bar rather than a desk. He stood on the backboard, keeping his eyes fixed on the second bus, which was still following, always just one stop behind.

He let his double-decker take him down High Holborn and deeper into the city’s history, past Chancery Lane towards St Paul’s, then along London Wall, which traced the path of the ancient Londinium’s battlements.

Knox could have stayed standing on the backboard as the bus took him further and further away from the West End, but constantly watching the second night bus follow him was making him impatient. He suddenly wanted to flush out and face the man from Soho Square, so as the bus slowed through a deserted junction he took a chance, jumped off the backboard, and started to run.

Cripplegate was a black hole all hours of the day, but especially at night. Once one of the most heavily populated parts of the City of London, it had been almost completely flattened by the Luftwaffe, and immediately after the war its residents numbered in the tens. It took Knox just a few seconds to disappear into the darkness that seemed to stretch away into eternity from the streetlights of London Wall, and only a couple more before the ground under him became uneven and he felt himself kicking rubble as he ran. He was sure he was making enough noise to be easily tracked, but he slowed down to make sure of it—and to stop himself slamming too hard into some unseen chunk of building or something else where it shouldn’t be.

After a hundred yards Knox’s instincts told him to stop, and he held his hands out into nothing. He caught his breath as his eyes adjusted to another level of darkness and he discovered he was teetering right on the edge of a chasm-like bomb crater.

He crouched down and inched his way round the rim of the crater, feeling with his hands and feet until he found a slab of wall that would hide him but also give him a clear view of his pursuer hopefully tumbling full-tilt into the abyss. He waited, and waited. He was tense. The fear and anger of Stockholm and the decimation of his home burned inside of him, and he wanted to take it all out on someone. But the longer he. waited, squatting in the dark, the more he started to wonder if he’d actually been followed at all.