Flooded with coffee, Dyer raked back through their few encounters. Marvar’s abrupt disappearance during the Summer Fields game – that must have happened after Samir’s corner kick set the ball rolling, as it were. When Dyer first met him beside the sandpit, Marvar was scribbling mathematical formulas in the sand, tantalisingly close to a solution. Their excited embrace on the touchline following Samir’s goal against Horris Hill would have occurred within hours of Marvar’s successful experiment. Small wonder his ecstatic reaction.

Yet Marvar’s face last night was drained. He had talked like a man under attack from every direction, who didn’t know which way to turn. In the lucidity of his despair he chose to confide in Dyer.

Both their sons had been bullied by the same boy. Was that the reason, though?

Something about Marvar’s behaviour at the Horris Hill match had stayed, unexamined, in Dyer’s mind. How he raised the subject of Rejas and kept returning to him. The policeman’s story fascinated Marvar. But not so pressingly as Dyer’s reasons for keeping the story to himself, refusing to publish.

Dyer could only guess that Marvar had longed for an honourable way to be relieved of his responsibility. His options were narrowing with each moment, he didn’t have much time. He was passionate in wanting to save Shula, but the one means that he could think of to achieve this was out of the question. He had to look for his answer elsewhere.

In his paralysed state, it was easy then to understand why Marvar should have sought the help of his mother’s God, a god he had hitherto not believed in. What he had been on his way to pray for in St Barnabas, when forestalled by Dyer, was to have the decision wrested from him.

In those circumstances, who do you trust to give you release? You can’t trust your government – or any government. You can’t trust your professor at the Clarendon, who has but the haziest notion of who you are. You can’t trust your wife, because she’s lying semi-conscious in a prison cell in Tehran. All you’re left with is a superannuated ex-journo you met at a school sandpit and once stood beside on a touchline. You have to trust someone like John William Dyer, author of A Social and Cultural History of the Lower Amazon Basin (OUP, 2001), a man who had nailed himself so stubbornly to the mast of his high principles that he sank a reasonably promising career by keeping mum.

Shortly after 6 p.m. Dyer drove to the Asselins’ to pick up Leandro.