But I wasn't finished yet. I used my hands to push me upright as if I was doing some kind of springing press-up. Somehow I managed the process slightly quicker than him, before vaulting over the banister on to the next set of steps, stumbling down them, ignoring the savage pounding in my head.

Once again he was right there with me, and I knew he wasn't going to give up, so, summoning up every last ounce of whatever feeble reserves of energy I had left, I jumped the whole of the next staircase in one, landed hard on my feet, swung round using the banister as support, and did the same thing on the next one, and the next, feeling a kind of delirious adrenalin-fuelled excitement at the prospect of escape.

And at that exact same moment the stairs stopped and I realized I'd missed the ground floor, and possible safety. Instead, I was in the basement.

Panting, I looked back up just as my pursuer arrived at the top of the last flight of steps. 'Oops,' he said playfully, waving the knife in front of him like a wagging finger. 'Bad move.'

A small part of me felt like giving up there and then. Admitting the fact that I wasn't going to make it out of there and throwing myself at his mercy. Except that I knew there wouldn't be any.

And it was only a small part of me. Self-preservation won through, and as he jumped down the last of the steps I turned and ran for the fire door in the corner – the only way out. I had no idea whether or not it was open, or where it led to, just relied on my instinct to live to keep me going. Running right into it, I pulled down the metal handle, felt it give, and half fell, half scrambled through into a cold and cavernous underground car park.

He was still with me, almost as if he was glued to my slipstream, but this time I took the offensive and turned and slammed all my weight against the fire door, catching him by surprise and trapping his knife arm in it.

But before I could do any real damage, he pushed from the other side and, being one hell of a lot stronger than me and with momentum on his side, he sent it flying open, and me stumbling backwards.

I turned and ran through the dimly lit, silent car park, not knowing where I could turn. Ahead of me was one of those big roller doors that I knew was either the entrance or the exit, but it was shut. My legs felt weak and I just couldn't seem to get the pace up to put any distance between us – the bastard was like some kind of automaton – and I'd barely gone twenty yards before he leapt on my back for a second time, sending me crashing into the concrete.

Sitting astride my back, he yanked my head up by the hair and I knew in an instant that he was going to cut my throat like some kind of animal. I bucked and thrashed as the knife suddenly appeared right in front of my face, and managed to pull free a hand. I immediately grabbed him by the wrist, forcing the blade away from me. I also jerked my head forward, trying to bite him, but his grip on my hair was too strong. This guy had the better of me, and both of us knew it. My arm was shaking with the effort of holding the blade away, and right then my life expectancy could be measured in seconds.

The sound of hydraulics interrupted our deadly duel, and a second later the roller door began to open. I think it surprised both of us because I felt his grip on my hair momentarily ease, which gave me the chance I needed. I sank my teeth into his knife wrist, biting down hard, knowing that while his arm remained in my mouth he couldn't use the blade on me.

He yelled and grabbed my hair again, tugging me backwards, but this time I wasn't letting go and I kept biting down, remembering something I'd once read about the strength of a human bite being something like two hundred pounds of pressure per square inch. I tasted blood and his yells became more urgent.

And all the time the roller door kept opening. It was now five feet above the tarmac and I could see the headlights of a big 44 just outside, waiting to come in. There was no way it wouldn't see us. I was going to make it. I felt a rush of hope, kept my teeth clamped on his wrist.

But then, in one swift, savage motion, he yanked his wrist free from my jaws. I clenched my teeth, waiting for the knife to slice across my flesh, but instead the weight lifted from my back, and a second later I heard his footfalls on the concrete floor as he ran back the way he'd come.

Exhausted and battered, I lay where I was, looking up at the 44 as it nudged its way inside before turning left and disappearing from view.

The driver hadn't seen me. Did this mean that my attacker was going to come back and finish the job? Was he just waiting?

I didn't hang around to find out. I ran wildly through the open roller door and up the ramp, hitting the fresh night air of the street and breathing it in as if my very life depended on it.

But my life depended on nothing any more. I'd saved it. Now I had to think about Jenny's.

I kept running up the dark, silent street until I came to an alleyway on my right. I turned down it and, exhausted, took refuge behind a pair of wheelie bins, leaning against a wall and slowly sliding down it until I was sitting down. I had to phone the police straight away and tell them what I'd just witnessed, so, after taking a few seconds to get at least some of my breath back, I reached into my pocket for my mobile.

And cursed. It was in my jacket, back at the apartment.

Something else too…my wallet. With all my ID in it.

Which meant they were going to know exactly who I was.

A part of me wanted to keep running. To put as much distance between me and Jenny's place as possible, knowing how close I'd just come to death. Another part wanted to go back and keep watch on it, hoping that I might be in time to see the two men leave and pick up any vital clues I could then give to the police.

As it happened, I could do neither. I was too exhausted, and for a full minute I concentrated simply on getting my breath back.

As my panting began to ease, I was suddenly jolted back to reality by the sound of a car moving ever so slowly along the street.

Jesus, they're still here. Looking for me.

I turned round, looking for a way out, saw only a high wall I was never going to be able to climb. I was stuck up a dead end. Knowing I was hopelessly exposed, I lifted up the lid of one of the wheelie bins and wriggled inside, landing loudly on a pile of stinking binbags.

The sound outside was muffled but I could hear the car stopping and knew that it was at the end of the alley.

A car door opened. Shut again.

I began to pray. I'd never really believed in God, but now that I'd arrived at this single most terrifying point in my life, I desperately begged forgiveness for any sin I may have committed and promised faithfully that if he got me out of this I would be a much better person. That I would give money to charity, help people… anything.

Stop. Don't breathe.

I could hear stealthy footfalls on the concrete. Approaching me. Something plastic in one of the binbags made a cracking sound beneath me and I clenched my teeth. The silence was killing me. Was one of them right outside now, knife in hand, getting ready to strike?

I strained, listening.

Silence.

The wait seemed to last for ever. Seconds ticking like dull, bored hours.

And then I heard the car door slam again and the car pull away.

I exhaled sharply, but didn't move. It could have been a trap.

Gradually I began to breathe more easily but I continued to lie exactly where I was, listening to the quiet of the night. At some point I think I even drifted off to sleep: I remember opening my eyes and getting a shock because I was still in darkness, and the smell was terrible, and my mouth felt like someone had been sandpapering it. At first I didn't know where I was. Then it all came back to me in a huge rush like some kind of horrible hallucination. Someone had tried to kill me, and they'd come very close to succeeding.