I was exhilarated suddenly. This man’s true colours were showing under the strain and I could be free of him.

‘I’ll keep it shut,’ I said. ‘For as long as it helps Olivia.’

That evening an envelope was delivered at our house. The note inside explained that I was Olivia’s friend, that we were very close and that it would be beneficial for me to visit. The likeness of the handwriting to Alec Kemp’s was so extraordinary that I thought at first Elizabeth had persuaded him to put pen to paper himself. But there was a separate sheet on which Elizabeth had written, ‘I’m sure this will do it. Please believe better of me. E. K.’

The following Sunday I took the note to All Saints and was let in through the gate. The hospital was a huge, stately building like a country house, with stained-glass windows above the entrance and sunlight pouring on to its soft-coloured stone.

They wouldn’t let me see her. Not because I wasn’t a close relative, but because she wasn’t, they considered, in a fit state.

In June they had her moved to Arden.

‘Alec wanted to get her out of the city,’ Elizabeth told me. I always tried to visit the house when she was there alone. ‘He’s very much afraid it will get out somehow that his daughter’s in an institution. He’s still hoping to stand at the next election.’

I knew I had a kind of ally in Elizabeth, but I was wary of her. She had clearly decided that for the moment her feelings for Olivia must override her loyalty to her husband. But I saw I had never really known her at all, and she was so conditioned to giving nothing away. I was growing more suspicious about the whole situation. Clearly there was something more seriously wrong with Olivia than the odd outburst of emotion and anxiety she had shown before the war. And all these things were now beginning to build into a sequence of events that I hadn’t identified before. I wanted to get to the bottom of it: her unhappiness before the war, her withdrawal from me over those years, and what it was that had tilted her so far over that she had to be speedily put away out of sight.

I knew, though, that I’d never get the answers direct from Elizabeth. Sometimes when she looked at me with those childlike blue eyes and gave her automatic smiles, I wondered what it would take truly to break her into honesty.

Olivia had been in Arden for two weeks when, with Elizabeth, I managed to get into the place for the first time. I had gone alone the week before, carrying with me Elizabeth’s forged letter, but they turned me away.

We went together on the sort of day which normally makes you feel glad to be alive. The sky was almost unmarked by cloud and there was a feeling of expectancy in the strong sunlight that I always associate with early summer. But sitting in the cab in which we travelled from Leamington Spa I was churned up inside with apprehension. As we passed under the stone archway at the entrance to the drive I felt as if my heart was going to explode. Even being a nurse, like most people I regarded places like Arden with a kind of flesh-creeping horror. The surface of the curving drive was so rough I was thrown from side to side on the back seat. I watched the place move nearer, a vast brick building, the edge of its roof sculpted into points, looking dark and impersonal.