Larssen asked for five minutes alone with me before we got started. The two detectives left us and I told him about my discovery of Mel’s secret phone – her link to Ben during their affair – and that I had surrendered it with my own phone at the front desk.

‘Naylor should have his people look at it,’ I said. ‘Maybe it will help to track Ben down.’

‘They’re going to want your wife’s normal mobile as well.’

‘OK. Why?’

‘The texts from Ben last night, when you were setting up the meeting between him and Mel at the shopping mall. There could be something in the phone records that they can use.’

He made a note to that effect on his pad, then capped his fountain pen and spoke quickly and quietly, laying out the rules of engagement: he would deal with questions, I was not to comment or respond unless he indicated it was OK to do so – and then only with short, factual responses that related directly to the question. There were to be no exceptions to this rule. I was to remain calm and courteous, not let them rattle me, and not introduce new theories about Ben’s whereabouts. That’s their job, not yours, he said with some force. Above all I was to say nothing about my relationship with Ben, Beth or my wife.

His rules seemed clear enough.

‘I don’t get it, though.’

‘Don’t get what?’ he said.

‘How they’ve got to this stage already. What evidence can they possibly have to justify arresting me?’

‘We’re about to find out, Joe.’

Naylor and Redford came back into the interview room and sat opposite us. There were butterflies in my stomach, but it felt good to have Larssen riding shotgun beside me. Redford pushed a button on the Dictaphone.

‘Interview with Joseph Michael Lynch commenced at 5.51 p.m., 11 October.’ She turned her dark brown eyes on me. ‘Please state your full name, date of birth and current address for the recording.’

She went through various formalities and the names of the other three people present in the interview room. Naylor reminded me again that I was under caution and that anything I said could be given in evidence, but it might harm my defence if I failed to mention something now which was used later in court. He gave me his we’re-all-friends-here smile.

‘So, Mr Lynch,’ he said. ‘You know why you’re here, correct?’

Larssen said: ‘My client is here because you arrested him.’

‘Of course,’ Naylor said. ‘I’m merely asking about Joe’s knowledge of the bigger picture.’

‘Please fill us in, detective,’ Larssen said.