And then Walt had volunteered, amongst a lot of other stuff that I really didn’t want to know, that Alexandra had been a habitual user of sleeping pills. Zopiclone, to be precise. He had seen it as his duty to ‘wean her off them’, but that didn’t mean she hadn’t still got a supply.

Unwin had said they’d spoken to her ‘this morning’. Where had that been, I wondered. On the phone? In Hastings? At a police station? And, as the case against Alexandra seemed to be building up, would she have been allowed to leave the police station?

I couldn’t help remembering one of the first things Alexandra ever said to me. ‘My mother’s going to kill herself. If I don’t kill her first.’

Was it possible that the boost of her new relationship with Walt had given her the confidence to remove the person who had so overshadowed her life? The person who had taken all the oxygen, eclipsed her own personality?

By bizarre synchronicity, just as these thoughts were going through my head, I had a call from Alexandra Richards.

I couldn’t stop myself from asking, ‘Where are you calling from?’

‘Home. Hastings,’ she replied on a note of bewilderment. I suppose it had been an odd question. She wasn’t to know I’d been visualizing her in a police station under arrest for murder.

But her thoughts proved not to be a million miles away from mine. ‘I’d been wondering if you’d heard from the police?’ she asked.

‘Yes. Detective Sergeant Unwin and Detective Sergeant Gupta came to see me. They’ve only just left.’

‘They came to see me this morning.’

‘At home?’

‘Yes. What did they ask you, Ellen?’

The enquiry sounded excited but not paranoid. I didn’t get the impression that Alexandra felt threatened by anything the police had said to her.

I told her that the sergeants had asked me about Ingrid’s use of sleeping pills. I also reported what her mother had said on the subject.

To my surprise, this didn’t seem to faze her. ‘Oh, I’d always assumed she did take them. I thought it was a hereditary thing, sleeping badly. Something I’d got from her.’

Alexandra was full of contradictions. At one level, she seemed to have hated her mother. At another, she seemed desperate – as she had with the folder marked ‘Alexandra’ – for anything that implied some closeness between them.

‘I presume,’ I said, ‘that the police asked you again about the events of that Tuesday evening, the night Ingrid died?’

‘Oh yes, we went all through that.’

‘Did you tell them about you staying in your car outside the flat till after midnight?’

‘Yes, I did,’ she replied blithely. ‘They reckon I was probably the last person to see her alive.’

Her tone suggested she didn’t see how guilty that made her sound. Surely it was only a matter of time before the police came back to her with a more targeted interrogation?

‘So, everything you told them was the truth?’ I asked.