‘Not quite the memory of Mummy giving them their Weetabix.’ She sees the look I’m giving her. ‘Sorry. Inappropriate. It’s just that when I met her she always seemed so – well – strait-laced.’

It’s odd being reminded that Marilyn knew Clare, however briefly. It reminds me of something that’s been nagging at me.

‘Can I ask you something?’

‘That sounds ominous.’

‘Did you really not realise Clare was my sister when she came to see Johnny? I know she called herself “Prince”, but you wouldn’t just let your boss have private meetings with a random Treasury official. You’d have checked her out. Someone would have given you the family connection.’

Marilyn stubs out her cigarette in the mug. There’s a small fizzle from the teabag that’s been sitting in the bottom since breakfast. She looks me in the eye.

‘Truthfully, I didn’t know, at first. But Clare mentioned it to Johnny, and Johnny told me.’

‘Johnny knew?’ Did he mention that in our interview? I can’t remember. I’m too stunned by this apparent habit Clare had of talking about me, rather than denying my existence – which is what I’d imagined she did. ‘Do you know what she said about me?’

She shakes her head. ‘Johnny mentioned it in passing. As I said before, and honestly this is true, he never discussed the detail of his conversations with Clare.’

‘She was leaking the tax credit policy. She knew she’d be in big trouble if anyone found out.’ I stare at the Rorschach blotches of the Expressionist print on the wall opposite. I am not sure what I see.

‘I could tell he was impressed with her.’

‘My sister had a knack of impressing powerful men. Something to do with learning to cope with our overbearing dad, I think. But why didn’t you tell me as soon as you knew the connection with me?’

There’s heat in my voice. I’ve been so desperate to find out every scrap I can of Clare’s life, and now it emerges Marilyn’s been holding back.

Marilyn’s reaction to emotion from me is to become icy. ‘I always assumed that if Clare wanted you to know, she’d have told you. And it wasn’t my place. I suppose I should have guessed you’d have fucked up your relationship with her.’

I wince and Marilyn thaws. ‘Sorry. I shouldn’t have said that.’

‘It doesn’t matter. But is there anything else you haven’t told me? Anything Johnny mentioned that they’d talked about?’

‘Nothing.’ She’s pissed off he seemingly had secrets with Clare he didn’t share with her.

‘Didn’t you have any suspicions, any inklings?’ Something flashes across her face. ‘I know you. You always have a theory.’

She clicks on her yellow Bic to light another cigarette. She hunches her knees up against her chest and takes a long draw.