‘I hope you have enjoyed your tour today.’ His shrewd, bright eyes considered them. ‘When you join the Metropolitan Police you will all be issued with a warrant number. It is a little-known fact that these numbers are consecutive and have always been consecutive since the force began. I hope you had a chance today to look at the exhibit dedicated to the brave men and women who have died in the service of the Metropolitan Police. Every one of them had a warrant number and you will, too.

‘The very first warrant number was issued to Constable William Atkinson in 1829 – number one. On his first day in the job, and the very first day that the Met walked the streets of London – 29 September 1829 – Constable Atkinson was dismissed for public drunkenness.’

Laughter. Sergeant Caine allowed himself an ironic twist of the mouth.

‘But I know that you will be a credit to the Met, and to the generations who served before you. Take care of yourself and each other. Thank you and goodbye.’

They gave him a round of applause.

After he had escorted them to the first-floor lift, he came back and peered at my neck.

‘Max, you’re the only person I’ve ever seen whose looks have been improved by hanging.’ Then, for the first time in my life, he briefly hugged me. ‘Welcome home. I’ll put the kettle on, shall I? Your mob still babysitting Mustapha Pee?’

‘Abu Din? No, somebody from in here is watching over him. SO15 – Counter Terrorism Command.’

‘So an apologist for terrorists is being looked after by the policemen who protect us from terrorists? Somebody’s had an irony bypass.’

He placed two mugs of tea on his desk. As always, his mug proclaimed BEST DAD IN THE WORLD. My one said NOT ALL WHO WANDER ARE LOST.

I took a sip. Strong and sweet. John Caine always gave me three sugars without asking.

‘I need to know where I was, John. We need to find the place they hanged Mahmud Irani – and Hector Welles – and Darren Donovan . . .’

‘And you.’

‘And me. Same kill site. Same location. And nobody at West End Central has got a clue. We’ve rented an academic, a historian from King’s College, and even he is drawing a blank.’

John sipped his tea.

‘Talk me through it,’ he said.

And so I did. All of it. From the moment the white van drew away to the armed guard outside Abu Din’s council house to the appearance of the black van. From the unimaginable muscle spasms of being shot by a conducted electrical weapon to the mystery ride to the kill site. I told him how I had fought for my life.

And I even told him the one thing that I had held back from everyone else. I felt the need to tell someone.

I told John Caine how I had aborted my hanging.

‘Hold on. You had a gun?’