Abu Din went off to address the followers who were gathering in the street. Edie and I went to the window and watched. It was the kind of shabby suburban street that looks grey and tired even in the middle of a blazing summer. But there was no mistaking the buzz of excitement that ran through it when Abu Din began to speak in Urdu.

‘Why didn’t they just do him straight away?’ I said.

‘Maybe their kill site was being used for a yoga class,’ Edie said. ‘Do you believe he didn’t see or hear anything, Max?’

I nodded. ‘If they knew enough to cover their registration plates, and if they knew enough to burn all forensics in the van, then they knew enough not to make all the usual dumb mistakes – like calling each other by their names or showing their faces in the presence of their victim.’

We walked out into the street.

Beyond the heads of the crowd of men listening to Abu Din – and they were all men – I could see the uniformed black cop who had been minding the street when the transit van bowled up. Beyond him, the young man in the wheelchair was back with the young woman who accompanied him. They still had their placard and the young man in the wheelchair held it up as Abu Din slipped from Urdu into English.

‘In the mighty fire much was revealed to me,’ he declared. ‘It was revealed that the black flag of Islam will fly above Buckingham Palace and it will also fly above Downing Street.’

‘Don’t hold your fucking breath,’ Edie said.

Skirting the crowd, we walked to the end of the street and introduced ourselves to the uniformed cop. Our people were still here, but not in great numbers and holding back. The SIO – DCI Whitestone, back where she belonged – the CSIs and the search teams had all been and gone on this grey street and now they were up at the London Gateway services on the M1, rummaging around the derelict container where Abu Din had been imprisoned.

We showed our warrant cards to the uniform. Up close he was far bigger than he had looked on CCTV and much younger. He couldn’t have been long out of Hendon. Rocastle, it said on his name tag. He was embarrassed he hadn’t done better when the transit van came barrelling down the road.

‘You did the right thing,’ I said. ‘You got out of the way. They wouldn’t have stopped for you or anyone else.’

‘Did you see their faces?’ Edie said. ‘Hear anything when they got out of the van?’

‘They had those masks on when I clocked them,’ he said. ‘The Albert Pierrepoint masks. There was a lot of screaming and hollering when they were getting Abu Din into the van, but I couldn’t tell who was shouting.’