After writing it down, he went back to sleep. In the morning, he picked up the sheet of paper that he had put on his bedside table between the photos, books and possessions, and read: ‘Ordinarily he took the train.’

Groggily, he belted on his dressing gown.

In the meagre light, the chill vacancy of Leandro’s room. On the draining board downstairs: two empty wine glasses, a white mug three-quarters full with cold coffee, Marvar’s barely touched pizza.

In Brazil, ‘pizza’ was slang for a crime which suffered no legal consequences. Marvar had committed no crime – so far as Dyer could tell. He must have shambled back to his digs in Merton Street.

Dyer drew the curtains, peered through the French window. The mist reeked out of the canal and shrouded the buildings. Over the neighbour’s fence and the grey tiled rooftops, the clang of bells. It could have been Belém – the narrow roads off the square and little two-storey houses painted in pastel colours, with front doors onto the pavement. But it was the energetic vicar of St Barnabas tolling him to morning service. Marvar yesterday had been on his way there, Dyer now recalled. He was dressed up for church, dressed to pray, and had paused with the smokers outside the OUP for a cigarette when Dyer strolled out of the fog.

The bells stopped, tossing Dyer back ashore in Jericho. Should he call someone? But who? He’d cross that bridge after breakfast. Once he had set down all that he could remember of his conversation with Marvar.

Despite his aching hangover, Dyer forced himself to the kitchen table, and, with a full pot of coffee beside him, started to write out the story before the details vanished into the mist. His return to England had coincided with the revelation that Microsoft, thirty years before, had inserted into every programme a device which allowed the US intelligence services access to your computer. It hadn’t required Marvar to remind him that the best way of safeguarding a secret was with pencil and paper.

Much of what Marvar had told him was too technical, and Dyer left out a lot; as well, he may have misremembered certain things. Still, it was a relief to be exercising his reporter’s muscles, to be writing, back in the flow. Over the past months, his mind had lost itself in the Cherwell’s weeds, but now it was on fire with what Marvar had said. By transcribing this onto sheets of A4 in shorthand, Dyer was making it real. Exactly what he would do with it, he had no idea. All he knew: Marvar’s story was unlike any he had heard.