Seawoll returned and told us that we would be continuing the interview in an adjacent room, one where the monitoring equipment was still working. There, we continued the time-honoured tradition of brazenly lying through our teeth while telling nothing but the truth. I told them that Nightingale and I had reason to believe, through an entirely conventional informer, that the group – because it had to be more than one person – who had perpetrated a series of senseless attacks in and around the West End would be based on Bow Street, and that we had been investigating there when we were ambushed by unknown assailants.

‘Deputy Assistant Commissioner Folsom is particularly worried about any threat to the Royal Opera House,’ said Seawoll. Apparently he was a bit of a connoisseur, having been introduced to Verdi soon after rising to the rank of Commander. A sudden attack of culture snobbery is a common affliction among policemen of a certain rank and age; it’s like a normal midlife crisis only with more chandeliers and foreign languages.

‘We think that the focus of activity may be on Bow Street,’ I said. ‘But as yet our investigations have discovered no tangible link to the Royal Opera House.’

By six o’clock we ended up with a statement of events that Seawoll could sell to Folsom, and I was falling asleep in my chair. I expected to be suspended, or at least warned that I was facing disciplinary action or an investigation by the Independent Police Complaints Commission, but it was just coming up to seven when they let me go.

Seawoll offered me a lift, but I refused. I walked up St Martin’s Lane shaky with tension and lack of sleep. The weather had turned during the night. There was a chill wind under a dirty blue sky. The rush hour starts late on a Saturday, and the streets retained some of their early-morning quiet as I crossed New Oxford Street and headed for the Folly. I was expecting the worst, and I wasn’t disappointed. There was at least one unmarked police car that I could see parked across the street. I couldn’t see anyone inside, but I gave a little wave just in case.

I went in through the front door because it’s better to face things head on and I was too knackered to walk round to the mews at the back. I was expecting police, but what I got were a pair of soldiers in battledress and carrying service rifles. They wore woodland DP jackets and maroon berets with parachute regiment badges. Two were blocking my way past the cloakroom booths, while two more were tucked away either side of the main doors, ready to catch anyone suicidal enough to attack two fully armed paras in the flank. Somebody was taking the physical security of the Folly very seriously.