Riots are rarely spontaneous. Crowds usually have to be assembled and provoked, and a conscientious inspector keeps a weather eye out for problems. Especially when his patch contains a riot magnet like Trafalgar Square. The only half-convincing lie I could think of was that somebody had attacked the Royal Opera House with a psychotropic aerosol, but I figured that might raise more questions than it answered. Not to mention trigger an inappropriate military response. I was just about to risk the truth, that a kind of vampire ghost had put the influence on the entire audience, when Neblett twigged exactly who it was he’d just smacked in the head.

‘Oh my God,’ he said, squatting down for a closer look. ‘This is Deputy Assistant Commissioner Folsom.’

Our eyes met across the twitching form of our senior officer.

‘He didn’t see you, sir,’ I said. ‘If you call an ambulance we can have him off the scene before he regains consciousness. There was a riot, he was attacked, you rescued him.’

‘And your role in this?’

‘Reliable witness, sir,’ I said. ‘As to your timely intervention.’

Inspector Neblett gave me a hard look. ‘I was wrong about you, Grant,’ he said. ‘You do have the makings of a proper copper.’

‘Thank you, sir,’ I said. I looked around. The riot had moved on – down Floral Street and into the Piazza, I reckoned.

‘Where’s the TSG?’ I asked.

The TSG are the Territorial Support Group. These are the guys that tool around in Mercedes Sprinter vans with equipment lockers stuffed with everything from riot helmets to tasers. Every borough command has a couple of these buzzing around their operational area, especially at closing time, and there’s a reserve force held on standby just in case of unexpected events. I suspected that current events counted as unexpected.

‘They’re staging on Longacre and Russell Street,’ said Neblett. ‘It looks like GT’s plan is to contain them around Covent Garden.’

There was a crash from the direction of the Piazza, followed by ragged cheering. ‘What now?’ asked Neblett.

‘I think they’re looting the market.’

‘Can you get the ambulance?’ he asked.

‘No sir, I’ve got orders to find the ringleader,’ I said.

A Molotov cocktail makes a very distinctive sound. A well-designed one goes crash, thud, whoosh – it’s the last, the petrol igniting, that’s going to kill you if you let it. I know this because before you graduate from Hendon you get to spend a fun-filled day having them thrown at you. Which was why Neblett and I both instinctively ducked when we heard them smashing into the tarmac less then fifteen metres down the road.

‘It’s kicking off,’ said Neblett.

Looking south, I could see a mob of rioters on the crossroads where Culverhay met Bow Street. Beyond them I saw flames reflected off blue riot helmets and grey shields.