‘We had to be careful about what we said to each other about our lives outside home.’ There seems to be an edge in his voice.

‘Obviously she was subject to the Official Secrets Act. And I guess you’ve got to be careful about all those rules against insider trading. Sis was a stickler for the rules.’

A hollow laugh. ‘Yup. Clare never broke the rules.’

Charles sounds angry.

‘Are you OK?’

‘Never been better, as you can imagine, with the boys waking up at night calling for their mum, making it impossible for me to get enough sleep to do my job properly – and with you ringing me up as some kind of a source for a story, rather than doing what any other brother-in-law might do, which is to come round to see his nephews and offer to help. Yeah, everything is great.’

His anger hits me like a physical blow. ‘Sorry. I’ve been a shit uncle. No excuse.’

I am at the junction of Whitehall and Trafalgar Square. On autopilot to return to the Palace of Westminster, via Horse Guards, I do a loop back towards the Mall. As I cross Whitehall, towards Drummonds Bank, a late middle-aged woman tut-tuts at the noise pollution I am generating with my conversation. I avoid catching her eye.

‘Look, Gil. I understand. Sort of. You have been a shit uncle. And you were a shit brother. At least in recent years. But Clare loved you. She was always talking about you. I assume you loved her too.’

‘I have been a prick. A total prick.’

‘Yes.’

I think he’s almost relaxing. It is as though a pressure valve has been released and some of the tension eased. ‘I was actually going to ring you later today. Something has happened that I needed to tell someone about. And even though you are a world-class A-hole, there is no one else I can share this with.’

I am surprised, and pleased. ‘Obviously I want to help if I can. What’s happened?’

‘We had the post-mortem back,’ he says. ‘I thought maybe you knew and that’s why you were ringing.’

‘I had no idea. But presumably there was nothing of interest in the pathologist’s report. St Thomas’s already told us she had a lethal blow to the head. The cause of death wasn’t in doubt.’

‘I’m not talking about the cause of death.’

‘What else?’

‘For a start, she had a bucketload of alcohol in her blood. Bottle and a half of wine.’

‘That can’t be right.’

‘It’s what the report says.’

‘But Clare –’

‘ – hardly drank, no. It’s odd. Especially for a woman who was six weeks pregnant.’

‘She didn’t drink in . . .’ As so often, my mouth has started speaking before my brain has finished processing. I rewind in my head what Charles has just said.

‘Pregnant?’

‘First trimester.’