When they’d set out from Jericho less than two hours earlier, Dyer couldn’t help feeling that Marvar was treading the line between deception and self-deception. His scepticism had not dissolved as Marvar described his football-shaped laser. It was hard for Dyer to suspend disbelief about a junior researcher from Tehran – who must have been under surveillance already, given the history of the Iranian nuclear programme – being able to make such a significant discovery, on a Friday evening on his own, without leaving any trace.

Dyer now made an about-turn.

Unlikely as it seemed, here was this solitary Iranian in his late thirties, in exile in this city of striped ties and black gowns and rain, naive, passionate, who never expected to crack nuclear fusion, but who might have succeeded where teams of scientists and government-funded organisations had failed.

It never ceased to amaze Dyer, the stuff we didn’t know, which it took the ingenuity or the sheer good luck of one individual to come along and clarify. Marvar’s fortuitous discovery – a new continent of knowledge entirely – was it so different from Cabral’s random discovery of Brazil after a storm at sea forced the admiral to turn westward?

Just for one instant, Dyer wanted to relish the outrageous outside chance that Rustum Marvar was more than a fugitive physicist in a dun-coloured greatcoat. He was a symbol, exquisite and indelible, like a figure on the stamps that Dyer collected as a boy to commemorate the moment when Alexander Fleming discovered penicillin, or the Wright brothers took off from the ground, or Marconi heard an impossibly far-away voice in the crackle.

A dense layer of cumulus lay overhead, an ice-floe of it. If you concentrated, you could see that it was moving. A fitful wind carried the smell of fresh cow pats and horse dung.

Dyer was uncertain how long passed before he heard himself say, ‘What do you plan to do?’

‘I don’t know,’ Marvar replied in a lifeless voice, speaking with his back to Dyer. There was something sad about him, like a man who had worked hard and still failed an exam. He took off his glasses and rubbed one eye and then another with the sleeve of his coat, and put his glasses back on. His movement had an excruciating slowness to it as he turned. ‘I really don’t know …’

Dyer knew that he would remember Marvar’s expression for a long time, the hollowness in his brown eyes. If Dyer expected them to reflect what Marvar’s eyes alone had seen, he was shocked. There was no pulse of light in them. Where elation should have been was a nameless, infinite dread.

‘… You see, in my country, everything evil is having the time of its life.’