Though Deyna seems not to have been irresponsible. According to witnesses, he hadn’t been speeding or driving dangerously and the police say there was no alcohol in his blood. He stopped as soon as he realised what had happened. He had a mobile phone and called 999. A nurse who had just finished her shift was walking past: she and Deyna put Clare in the recovery position while they waited for the ambulance. Her head had been knocked into the kerbstone and bashed hard.

‘Why wasn’t Mummy wearing her helmet?’ says a small voice from the floor. While I have been talking to my father about what happened, I haven’t noticed the nine year-old at our feet. He’s been absorbing every word. ‘Mummy always wears a helmet.’

This doesn’t seem the right time to tell him that even seemingly infallible beings like his mum are capable of mistakes. ‘I don’t know Sam,’ I say. ‘These things happen.’ I’m not entirely sure he knows who I am. To him, ‘Uncle Gil’ is probably less significant than Father Christmas – and doesn’t deliver presents.

‘No they don’t!’ he shouts. ‘She never forgets the helmet. Luke and I aren’t ever allowed on our bikes without one.’ He’s inherited his mother’s furious logic.

‘We all forget things sometimes.’

‘Mummy never does.’ He shakes his head, determined. The person who kept him and his brother safe is not here to explain and make things right. Everything is confusing. The helmet is the key to everything, Sam knows.

‘He’s young,’ Uncle Jake soothes. ‘He can’t really grasp it.’

‘Do you think we can?’ We’re all out of our depth.

‘We should be sitting shiva,’ Jake nags. For him there is comfort in tradition, the low stools and muttered prayers of a ritual that half the family practice and the other half – my half – despise.

‘For Clare?’ Dad says scornfully. ‘She didn’t believe in any of that . . .’ The words ‘mumbo jumbo’ are unspoken.

He’s right. Clare got that from him: remorseless rationality, a kind of religion of its own, everything explicable through the scientific method. No mysteries, just problems waiting to be solved.

‘But the burial, Bernard.’ Jake will not let an argument go either. ‘It should be tomorrow. We can’t wait.’

‘There has to be an inquest,’ Dad insists. ‘Because . . .’ He trails off, sighs, then starts again. He is not a man to shy away from difficult facts. ‘Because of the accident. We can’t get a death certificate until after a post-mortem examination.’

Jake shakes his head. ‘You can’t wait so long.’ He takes a beigel and bites into it. A piece of egg drops down his shirt front. ‘There must be something you can do. With your connections?’

‘Maybe . . .’ Dad says uncertainly. I detect a crack in the atheist’s fortress, an atavistic desire to expedite the burial. ‘But my connections are not exactly current.’