‘You have arrived,’ said the voice, and the app changed to show the tag was just twelve yards away, with a big arrow pointing to the left.

I didn’t stop the Skoda but drove on slowly past.

Half hidden behind a tall hedge, and with high, elaborate, wrought-iron gates firmly shut across the driveway, was a large house, more like a mansion, with two swanky cars just visible on the gravel in front of the double-width front door. And there was an intercom system on the wall next to the gate.

‘Blimey,’ Chico said, with his big eyes wide. ‘He must be doing bleedin’ well.’

Yes, I thought, but how many other people is he bleedin’ dry to afford it?

‘Okay,’ said Chico. ‘So we know where he lives. What now?’

I turned the car round in the turning circle at the end of the road.

‘Use my phone to take some pictures of his house.’

Chico clambered through into the back seat and snapped away as I again drove slowly past. But Park Edge was one of those places where unfamiliar cars driving by at slow speed, with the occupants staring out the windows taking photographs, would quickly get reported to the police, so we didn’t linger any longer than necessary.

However, I pulled into a garage forecourt just down the road.

I took my phone back from Chico and used the app to remotely switch off the NeverLoseIt tag. I didn’t want it beeping and giving away its position, as it would certainly do when it realised it was tracking somebody else.

I changed the phone back to my own ID before scrolling through the photos Chico had taken of Valance’s house.

‘Well done,’ I said. ‘They’re great.’

‘What are you going to do with them?’ he asked.

‘I thought I might send one of them to Valance’s mobile number with the caption: If you burn down my house, I’ll burn yours down too.’

‘Is that wise? Especially from your own phone.’

‘Probably not. But I want him to realise that I now know where he lives. I might just send a picture of his house without the caption. He’ll have to work out what it means.’

‘And what is that exactly?’ Chico asked.

‘Mutually assured destruction. MAD. The deterrent formula that had mostly kept the peace between the Russians and the Americans since atomic bombs were invented.’

And long may it do so, I thought.

‘But won’t you also be giving Valance your phone number?’

‘I certainly will, but it’s hardly a secret anyway. For years it was on my website so potential clients could contact me. I’m sure he would have had it already. And I don’t think it’s a bad thing anyway. Bit like the Red Telephone Hotline.’

‘Eh?’