She thought of him at Christmas the year before last. They’d spent it in Edgbaston with Corinna and Josh. It had worked really well; they’d all had proper time together, and Len had made trips over here to see her grandparents. In the evenings, after Josh had got him into his PJs, Peter had come to the dining table to say goodnight. Those legs – in tight jersey bottoms printed with aliens and flying saucers, they’d been long and spindly as breadsticks. She’d looked at Corinna, who’d folded her lips together to contain the laugh, the I know, it’s too much of maternal love.

‘It’s an hypothesis – a theory,’ said Patel.

She gave him a look: I know what a fucking hypothesis is.

‘That having killed his wife in the heat of the moment, Mr Legge came to himself, realized what he’d done and knew he couldn’t bear his son to know. But knowing also that he couldn’t actively kill his son – the moment had passed, whatever had led him to kill Mrs Legge – he set the fire not only to destroy evidence but in the hope that his son, who he knew to be asleep upstairs, would die from smoke inhalation without ever waking up.’ He laid it in front of her, formal as a barrister.

‘No,’ she said. ‘Not possible.’

‘As Mrs Legge’s closest friend, were you a person she confided in? Shared her secrets with?’ Thomas.

‘Yes, when there were any.’

‘What sort of things would they be?’

Robin took a silent breath, tried to calm the storm in her head. Arson. ‘Rin’s dad was an alcoholic,’ she said. ‘He wasn’t physically violent, nothing like that, but he was useless, Trevor. Worse than. Her mum was basically a single parent when Rin and Will – her brother – were growing up. Oh god – does Di know?’

Thomas nodded.

‘It was the full Monty with him: sleeping rough round the coach station, going AWOL for weeks at a time, getting beaten up. Lost his teeth. Mrs Pascoe brought up Rin and Will on her own and she’s a nurse so they never had much money. It’s why Rin didn’t go to uni – she was more than capable, she was with me at the grammar school, she got two As and a B at A-level. She wanted to start earning straight away, though, help her mother.’ She remembered Corinna walking out of the British Heart Foundation in town, that Yorkshire accent: ‘You know what, pet? I’ve ’ad it up to me neck with cast-offs. Time to get a job.’

‘How about more recently than that? Was there anything on her mind? Anything worrying her?’

Robin tried to think. ‘No. Nothing that would even remotely … They would have liked another baby.’

‘But they didn’t?’