Dyer heard this without commenting, as a doctor listens to a hypochondriac rehearse their symptoms. Little mental effort was required to see that Marvar could be an eruptive, discomposed personality, with extreme reactions to people and situations.

‘The truth is, I never expected it …’

His voice was disincarnate. His heart was in a state of considerable nervous excitement over the fate of his wife and daughter, but Dyer had the impression – once again – that it overspilled with other passions.

‘… I never expected to have results …’

‘I’m sorry,’ Dyer said finally, after Marvar had jumped to his feet. ‘What are these results you’re talking about?’

Marvar stood stooped by the window, white mug in hand, a faraway glaze in his eye. The dense mist, evocative and deceiving, drifted over the empty boatyard, now and then thinning to reveal the canal. The tinder path opposite, with barges tied up; along the near bank the backs of narrow lawns sloping up to Edwardian houses, and modern developments, gardenless, with balconies and sheer facades like Venetian palazzos.

‘Look, how lovely it is over there.’ He turned his lost face to Dyer, as if chasing his last chance for joy. ‘Let’s go out.’

In between clangs from next door, the bells of St Barnabas chimed twice. On a frost-hardened field in Brackley, the whistle had gone and Leandro and Samir would have started playing – with neither of their fathers watching, it depressed Dyer to think, as he went to retrieve Marvar’s overcoat.

Marvar stood abstractedly putting his coat back on while Dyer telephoned Silvi Asselin to tell her that he couldn’t, after all, make it to the match this afternoon, nor could Samir’s dad, and might she be able to give their two boys a lift home for tonight’s sleepover?

Silvi was determinedly good-natured; Gilles was always cancelling at the last moment. ‘You’ll miss the tea,’ was all she said. The match teas at Winchester House were the best.

They crossed the bridge and walked along the towpath, Marvar every now and then glancing back. The canal flowed slowly, darkly; twigs and bottles were trapped on the surface like tar. Nothing seemed reflected in it, no birds, no clouds, no streak of sunlight. Ducks submerged and rose, shaking their heads near the far bank. Smudged by the thinning mist, solitary men crouched beside black nets fishing for tench.

As they walked, Marvar started to tell Dyer a curious – no, a fantastic – story. He would not have spoken so freely before coming to England. But in the more libertine atmosphere of Oxford, he had discovered that you can say what you like and the sky doesn’t fall in.

They were passing a moored-up barge when Marvar turned to him. ‘What do you know about nuclear fusion?’