‘Wait.’ Sarah held his hand firmly. ‘I did have a point. I read that psychopaths lack the capacity to experience limerence, because they don’t produce enough oxytocin.’

‘Isn’t that the baby hormone?’

Sarah nodded. ‘It’s often referred to as the attachment hormone. We feel it when we bond with other people and even with animals. It’s released when mums feed their babies, when we have sex and even when we stroke a dog.’

Jameson sat down again, intrigued. ‘So psychopaths don’t get attached because they can’t feel that high?’

‘It’s just one hypothesis, but it might be why psychopathic partners can walk away from a relationship without looking back.’

‘They really are wired differently.’

‘Seems that way. Although whether it’s in response to genetic factors or environmental conditioning … that’s something Augusta would probably know.’

‘I’ll probably feel like a bit of a gooseberry when she gets here, with you two nattering on about psychopaths …’ He checked his watch again. Her train had arrived fifteen minutes ago. ‘I’ll give her a call. Maybe she’s gone to the wrong bar.’ Before he could do so, a broad-shouldered man approached their table; his black suit, polished shoes and general demeanour screamed policeman.

‘Mr Jameson, Dr Mendax – DCI Beardsley.’ He flashed his warrant card, then placed it back in his jacket pocket. ‘I believe you’ve just given a statement to my colleagues over in Sovereign Square car park. You mentioned a man called Stuart Rose-Butler? I’ve been looking for Mr Rose-Butler in connection with a case I’m working on. Could you spare me a moment of your time?’

Jameson felt a flicker of something, but he couldn’t put his finger on it. But he and Sarah had indeed reported Stuart to the officers in the car park.

‘Take a seat,’ said Sarah, clearly happy to help.

‘Could we discuss it at the police station?’ The DCI looked from Sarah to Jameson. ‘It’s only a five-minute walk.’

‘We’re waiting for someone.’ Jameson felt an echo of suspicion.

‘You can text her and ask her to meet us there, can’t you?’ said Sarah.

‘She should be here by now.’ He stood, peered out of the window and scanned the concourse again. Four businessmen walked past and into the Brazilian restaurant on the opposite corner. There were three students in skinny jeans and trainers at the end of the dock, unlocking bikes from the railings. But no sign of Augusta.

He took out his phone and called her. It went to voicemail.

‘It’s me. Did you catch the four fifteen? We’re still in The Lock.’ He looked at Sarah. She was standing with her jacket on and was chatting with the policeman. ‘But we’re heading to the police station to answer some questions about Stuart.’ Sarah would do whatever it took to catch the perpetrators; he couldn’t blame her.