Cage’s mouth tightened. ‘Chapter and verse. This country has the most restrictive knife laws in the world. Not that you’d know it from all the kids in A&E with their stab wounds, their guts hanging out. Look, I don’t sell flick knives, sword canes, butterfly knives, throwing stars or gravity knives, OK? I sell to collectors. I’ve got a licence. And I want to keep it. That’s why I got a photocopy of his ID, all right? Now, do you want to talk about him or me?’

We were running the ID Cage had brought us through the Police National Computer. It was a UK driver’s licence for what the PNC database would recognise as an IC1 – a male of white-skinned European appearance. There was a face and a name and a DOB. A young man around thirty with thinning hair. An attempt at a smile that never quite made it past the hint of a sneer. And there was an address. Right at the edge of the city.

‘Do you buy this ID?’ Gane said to Mallory. ‘Bob’s up to his neck in security architecture online but he doesn’t have a fake photo ID? You know how many sites there are flogging fake photo IDs?’

‘Not good ones,’ Cage said. ‘It’s easy to get a bad one. Not so easy to get a good one. That’s the real thing. Or better than anything I’ve ever seen.’

‘Did he know his stuff?’ I said.

‘How do you mean?’ Cage said.

‘Did he know what he was buying?’

‘He was very specific. The men who come in Second Front are collectors. They all know their stuff. He wanted a Fairbairn-Sykes commando dagger. Prepared to pay top dollar. I sourced it for him. Found a nice Second Pattern F-S made by Wilkinson.’

‘And where did you get it from?’ Mallory said.

‘I’m not telling you,’ Cage said, folding his arms.

Gane made a move towards him as Whitestone appeared in the doorway.

‘We’ve got him,’ she said.

The chief super walked into MIR-1, her face tight with tension beneath the helmet of blonde hair. It could have been Mrs Thatcher getting ready to send the Task Force to the South Atlantic, horribly aware that this thing could go either way.

The crowd parted for her and she did not look at any of us until she came to Edie Wren, sitting on her desk at her workstation, a man’s face on the screen behind her, like something she had just caught.

‘What have we got?’ DCS Swire said.

The face on the screen was the same photograph as the one on the driving licence but now it was life-size; now you could see the wary spite in the eyes, the thin scars from ancient acne, the way he had brushed his hair to cover the growing expanse of forehead.