Perez nodded, but what could he know of life in a smart English university? The nearest he could come to it was being sent from Fair Isle at the age of eleven to board at the Anderson High in Lerwick. Then Duncan Hunter had been his ally and protector, but he couldn’t imagine being friends with the man now. They rubbed along together because of their responsibility for Cassie.

Caroline continued to speak. ‘We shared a flat in the second year and a house in the third. One night at a party Eleanor named us the Three MsKeteers – she was going through a feminist phase – and that stuck. I was going out with Lowrie then, but I carried on living with the girls and he was a kind of permanent fixture. We were all very close.’

‘And you kept in touch even after you left university?’ Perez had never made those sorts of close friendships. He wasn’t the kind of policeman who used colleagues as a surrogate family.

‘When we graduated the three of us were based in London. Polly started her postgrad training – she’s a librarian – and I was doing my PhD. Eleanor found work as a runner with ITV. So we just went on living together, sharing a grotty flat. Lowrie got a job in Edinburgh, but he came down when he could. We were poor as church mice. It wasn’t very different from being students.’ She gave a little smile. ‘Though Nell was subsidized big-style by her mother and, when she got fed up with slumming it, she’d go home for a weekend of comfort. Lowrie was earning, so I got treated to nights out when he came to stay. I suppose it was really only Polly who found it tough going financially. Not that it stopped the rest of us moaning.’

Perez listened and tried to picture these three young women in their flat in London at the beginning of their careers. He said nothing to hurry on the story. He was more use here than he would be out helping the search team.

‘We did well in our own fields,’ Caroline continued. ‘Moved out of the slummy flat. Lowrie got a promotion to London and he and I set up home together. Eleanor was a rising star in ITV. Polly qualified and got a job first in a local-authority library, then in the Sentiman, where she still works. That’s a weird place in Hampstead. It keeps the records of the UK Folklore Society, tales of morris men and legends of the Green Man. You know the sort of thing.’

Perez thought he had no idea. ‘And ghosts?’

Caroline looked at him sharply. ‘I don’t know anything about that. You’d have to ask Polly.’ She paused before continuing her story. ‘For a while she and Nell shared an apartment, but then Ian Longstaff swept Eleanor off her feet and into his house in South London and Polly found a nice little flat of her own not far away.’ She paused. ‘I suppose we grew up.’