‘So, Mr Booth, you said that you have some information about Margaret Krukowski.’

It took Booth a while to speak. Perhaps he was expecting the officers to ask him direct questions.

As he waited, Joe looked at him, taking in the details. His clothes. Denim jeans and a checked shirt and knitted sweater. Those sturdy trainers that could act as walking boots. Booth was wearing a green fleece too, though it was warm in here. He wouldn’t be a man to feel the cold, but it would have taken movement to get it off, and still he wasn’t moving much. A face moulded by the weather, and eyes like slate.

‘Margaret Krukowski was a prostitute,’ Booth said. ‘Not recently, as far as I know, but years ago. I only just discovered – when Kate said it – that Dee Robson was a sex worker. And suddenly it seemed important.’

Sparks were firing now in Joe’s head. So we’re not looking for a man who hates women, but a man who hates prostitutes. He wondered what Vera would make of the news, then thought she might not be surprised that church-going Margaret had once worked in the sex trade. The boss had said from the beginning that they needed to uncover Margaret’s secret.

‘How do you know that, Mr Booth?’

He took a deep breath. ‘Because I used her services. Regularly, over a number of years.’ Joe thought the man would stop there, but he continued to speak. Joe thought that a priest taking confession might feel like he did now – curiosity flecked with embarrassment and distaste. Booth continued: ‘I was a newly qualified teacher, awkward, shy. Needing a relationship, but not sure about how to get one. A kind of joke with the other musicians. One of them gave me her number.’ Even now he seemed to be blushing at the memory. ‘I got drunk one night and phoned her.’ He paused. ‘She didn’t call herself Margaret, of course, and never mentioned a second name.’

‘What did she call herself?’ The room was on the ground floor, and outside there was the background rumble of traffic.

‘Anna,’ he said. ‘She told me she was Polish, but I didn’t believe that. Her accent was English. Perhaps she thought the story would make her seem more exotic.’

‘She married a Polish man.’ Joe felt an urge to stand up for the woman, despite her chosen profession. ‘So it was almost the truth.’

‘Well, of course she never told me that she’d been married.’

‘The marriage didn’t last long,’ Joe said. ‘Only a couple of years.’

‘I was probably with her longer than her husband.’ Booth leaned back in his chair and shut his eyes. The notion seemed to give him some satisfaction.

‘Where did she live?’