‘And I would then have to agree to dissolve our prenuptial agreement and sign a post-nup in its place, with various clauses covering total forfeiture of assets and guardianship of Alice in case of further adultery.’

‘Using Mel as the messenger,’ I said.

‘Yes. To show who was the boss.’

‘But you knew what he was planning anyway, because you were monitoring his calls, texts and emails.’

Beth said: ‘We knew it was coming, we just didn’t know when. Turned out it was one boring average Thursday evening at a shitty little hotel off the North Circular.’

No wonder Ben didn’t want to talk when I saw him in that underground car park. He already had a lot on his mind.

I realised something else.

‘When he gave that ultimatum, you were listening in to the conversation, weren’t you?’

She nodded.

‘Every word.’ She gestured at me with the shotgun again, the twin black barrels pointed at my head. ‘And then who should walk in at the end, right into the middle of everything like Forrest bloody Gump?’

‘Me.’

‘Poor old Joe, about ten miles off the pace as usual, stumbling into the game without even realising it was in play.’

‘I got there in the end.’

She looked amused by that.

‘So what was it that finally clicked for you?’

‘The selfie on Mel’s secret phone – the one with her topless in the kitchen. The one you showed me at the pub on Sunday. Something about it bothered me, and I couldn’t work out what. It was only on the train back here today that I realised.’

‘What?’

‘It wasn’t where it was taken, it was when. All the date and time data had been deleted from the image, but the kitchen noticeboard was in the background of the shot, and William’s Superstar certificate from school was on it. He didn’t bring that home until Thursday evening, which meant that picture had to have been taken after she’d supposedly had this massive bust-up with Ben that sent him over the edge. So I knew Mel was involved in something, that she was still lying to me. I hadn’t put you two together yet, but I knew the picture was a lie.’

‘Indeed,’ she said with a half-smile. ‘Like all the rest of those naughty pictures. Pictures usually lie better than words.’

‘Then there was the escort agency. They were keen to get their repeat booking.’

‘Ah, yes. Young Jules.’

‘They sent me his picture, just a head and shoulders. But as soon I saw it, I knew.’

‘You knew what?’

‘He was the man I saw at the country park on Monday morning. Not Ben, but his double. Same height, same build, same hair. Put Ben’s jacket on him and he’s a dead ringer for your husband, or at least he was from fifty yards away.’