But the one in the back was quick. He was already swinging open the door and coming out with what looked like a gun in his hand. I didn't have time to take a closer look. Instead I retreated three steps and squeezed the trigger as he came into view. I got him somewhere in the upper body but still he kept coming, and fast. I continued firing, holding the gun two-handed, teeth clenched against the noise that was exploding in my ears. The momentum of the bullets forced him backwards, driving him into the door. He did a manic, confused dance to the tune of the gunfire, his arms and legs flailing, and angry red spots appeared like pox on his crisp, white shirt.

And then the magazine was empty and everything stopped as suddenly and dramatically as it had begun.

For a second he remained upright, holding on to the door for support, the energy almost visibly leaking out of him. Then he sort of half fell, half sat down, losing his grip on it in the process. He looked down at the blood on his shirt, and then at me, and I got a good look at his face, which I didn't want at all, because it was young, maybe late twenties, and his expression was all wrong. What I mean is, it wasn't the expression of a sinner. There was no defiance there; no rage. Just shock. Shock that his life was being stolen from him. He looked like a man who didn't think he deserved it, and that was the moment when I should have known I'd made a terrible mistake.

Instead, I turned away from his stare and reloaded. Then I stepped forward and shot him three times in the top of the head. The mobile phone he was carrying clattered noisily to the ground.

I dropped the gun into my jacket pocket and turned towards Danny, who was now bringing the car round.

Which was when I saw her, maybe fifteen yards away, standing in the light of the rear firedoor, a bag of rubbish in each hand. No more than eighteen and looking right at me, still too shocked to realize that what she was witnessing was real. What do you do? A movie pro would have taken her out with a single shot to the head, although there was no guarantee I'd even have hit her from where I was standing. And anyway, I'm not interested in hurting civilians.

Her hand went to her mouth as she saw I'd seen her, and I knew that any moment she was going to let out a scream that would probably wake the dead, which, with the dead only just being dead, I didn't want at all. So I lowered my gaze and hurried round to the passenger door, hoping that the gloom and wet had obscured my features enough to make any description she gave worthless.

I jumped in and kept my head down. Danny didn't say a word. He just hit the pedal and we were out of there.

It was 9.04.

The journey to our first change of transport took exactly four minutes and covered a distance of approximately two and a half miles. We'd parked a Mondeo in a quiet piece of Forestry Commission land earlier that day. Danny now pulled up behind it, cut the engine, and got out. I leaned under the passenger seat and removed a full five-litre can of petrol which I liberally sprinkled over the car's interior. When it was empty, I got out, lit a book of matches, stepped back so I was well out of the way, and flung them in, followed by the murder weapon and the two-way radio I'd been using. There was a satisfying whoosh as the petrol ignited, followed by a wave of heat.

When they came across the mangled wreckage it wouldn't tell them anything. We hadn't left any fingerprints and the car itself would be almost impossible to trace. It had been stolen in Birmingham six months ago, given new plates and a respray, and stored in a lock-up in Cardiff ever since. In this line of business, you can never be too careful. Contrary to popular belief, most detectives couldn't detect a heartbeat on a speed addict, but you never know when you might be up against the next Ellery Queen.

We now followed a pre-arranged route for four miles through a mixture of B and single-track roads and it was 9.16 when we pulled into the car park of Ye Olde Bell, a busy country pub on the edge of an affluent-looking commuter village. Danny drove up to the far end and stopped behind a burgundy Rover 600.

This was where we parted.

'Did that girl get a good look at you?' he asked as I opened the door. They were the first words he'd spoken since the shootings.

'No, we'll be all right. It was too dark.'

He sighed. 'I don't like it, you know. Three murders, and now we've got a witness.'

Admittedly it didn't sound too good when he put it like that, but at the time there was no reason to think that we weren't in the clear.

'Don't worry. We've covered our tracks well enough.'

'There's going to be a lot of heat over this one, Dennis.'

'We both knew that when we took the job. As long as we keep calm, and keep our mouths shut, we won't feel any of it.'

I gave him a friendly pat on the shoulder, and told him I'd call him the next day.

The Rover's keys were behind the front driver's-side wheel. I got in, started the engine and followed Danny out of the car park. He turned south and I turned north.

And that should have been that, but tonight was not my lucky night. I'd barely gone three miles and was just short of the turning that would take me back to London when I hit an improvised roadblock. There were two Pandas with flashing lights at the side of the road: officers in fluorescent safety jackets were milling about a BMW they'd already stopped. My heart gave an initial jump but I quickly recovered myself. No reason to worry. I was a man on my own, unarmed, driving a car that had never been within five miles of the Traveller's Rest, and they wouldn't even have the vaguest description of me yet. The clock on the dashboard said 9.22.

One of them saw my approach and stepped out into the road, flashing his torch and motioning for me to pull up behind the other car. I did as I was told and wound down the window as he approached the driver's side. He was young and no more than twenty-three, and very fresh-faced. They say you can tell you're getting old when the coppers look young and I could just about have been this kid's dad. He looked really enthusiastic as well. That wouldn't last. A second officer stood a few feet behind him, watching, but the other two were preoccupied with the driver of the other car. None of them appeared to be armed, which I thought was a bit foolish under the circumstances. I could have run this roadblock and they wouldn't have had a chance. I still could.

'Good evening, sir.' He leaned down into the window and gave me and the car a gentle once-over.

It always pays to be polite. 'Evening, officer. How can I help?'

'There's been an incident at a hotel called the Traveller's Rest on the A10. About fifteen minutes ago. You haven't come that way, have you?'

'No, I haven't,' I told him. 'I've come from Clavering. I'm on my way to London.'

He nodded understandingly, and then looked at me again. You could tell that for some reason he wasn't entirely convinced, although I don't know why. I'm not the type who arouses suspicions. I genuinely look like a nice guy. There shouldn't have been any alarm bells.

But there were. Maybe I'd just met the new Ellery Queen.

'Have you got any identification, sir? Just for the record.'

I sighed. I didn't want to have to do this because it could well cause me a lot of long-term problems, but I didn't see that I had much choice.

For a split second I baulked. But a split second was all I had.

Then I reached into my pocket and removed the warrant card.

He took it, inspected it carefully, looked back at me, then back at the warrant card, just to double check, probably wondering why his instincts were so wrong. When he looked back again, he had an embarrassed expression on his face.