As I feel my way out I'm assailed by more thick waves of choking black smoke as it pours up the stairs. There's surely no means of exit down there, which doesn't leave me much in the way of alternatives. I can feel panic rising in me, but I force it down and stagger blindly away from the stairs along a short corridor. I bang into something and stumble, only just managing to regain my footing. Through the haze, I see it's the prone figure of my interrogator, and he's unconscious. I won't be getting any answers out of him now, and there's no way I'm going to make it out of here carrying him, so I step over him and keep going.
There's a door at the end of the corridor and I open it, grope my way through, then slam it shut behind me. I'm in what appears to be a storage room. There are various bits and pieces – mainly boxes, and the occasional solitary item of furniture – piled high against all the available wall space, but my attention is immediately drawn to a large aluminium beer barrel standing in the centre of the room. I feel a rush of relief. It stands directly beneath an open skylight. Someone, it seems, has already made good his or her escape from the building this way. It's got to be the girl. I hope so.
I am exhausted, panting, breathing in acrid smoke, running on empty, but a desperate desire for fresh air drives me on and I clamber onto the barrel, reach up on tiptoes and just about manage to get a decent grip on the edge of the frame. I heave myself up, push my head through the gap in the window, and gulp down the fresh, warm summer air.
An explosion comes from somewhere below me, and the whole building shakes. Christ, what are they storing in this place? Dynamite? I'm not out of either the frying pan or the fire just yet. Using my arms as leverage, I drag the rest of my body through the gap until I'm lying on the tiles of the warehouse's sloping roof, facing out towards the canal and the buildings on the other side. Joggers and shifty-looking kids in school uniform are lining the towpath on the opposite bank, staring towards the inferno in front of them, and I can see Lucas's car parked up on the pavement on the bridge over the Kingsland Road, with the hazards on. He's stood beside it, and when he spots me he waves enthusiastically like I'm the long-lost cousin he's been waiting for in Airport Arrivals. He's at least forty yards and a very long drop away. At the very least, I think he ought to be looking for a ladder.
I roll down the slope of the roof until I reach the guttering on the edge, and look down. I'm right about the drop – it's far too high for me to jump, even with my training. Below me I can see smoke billowing out of windows and flames licking the walls on the ground floor. The wheelie bin in which I deposited the guard is completely engulfed by fire, and I wonder whether he escaped or whether, more likely, he's another person who's been killed today.
I can hear fire engines approaching from several different directions, but I'm in no position to wait for them. An old building like this one is going to come down fast. Already I can feel the tiles beginning to grow hot.
I turn my back on Lucas and make my way along the tiles until I reach the western edge of the building. The roof of the adjoining property is about ten feet away. That's a long way when you're jumping at height, but if I make it I know I'm home free because I can see it's got a two-storey extension sticking out the back, meaning that I can get back down to ground level without too much difficulty.
There are men in grubby overalls staring up at me from the yard down below. 'You're going to be all right, mate!' yells one, which is easy for him to say, I think.
Thin trails of smoke are now coming through the gaps in the tiles. Not long now until the roof collapses. From somewhere down below I hear another explosion, and once again the building shudders, as do I, almost losing my balance and heading for the ground quicker than I'd anticipated. Through the gap between the two buildings I see a police car pull up and an officer jump out, holding a radio to his mouth.
I take a few steps backwards, moving off the guttering so that I'm standing at an angle on the sloping, smoking roof, and then I make a run for it. Two seconds later, I'm sailing through the air, legs flailing as I try to maintain my momentum. My feet land on the edge of the other roof. One slips and kicks out into space, but my hands scrape at the tiles, and before I know it I'm rolling down the roof in the direction of the two-storey extension. I roll straight off, one hand grabbing a piece of guttering to ease my fall, and somehow manage to land on my feet on the extension's flat roof. I run across it, feeling more confident now, and do a single hanging jump that lands me in the burly arms of two of the overalled workmen. 'It's OK, mate, you're safe now,' says the one who offered me the encouragement earlier, but he doesn't know the half of it. I'm not safe until I'm well away from this place.
I cough violently, and someone thrusts a bottle of water at me. I take a long drink.
'You need to sit down, mate,' says the one who gave me the water, putting an arm round my shoulder.
'Is it a brothel in there?' asks someone else.
'I've got to run.' I wipe my mouth. 'Is there a back way out of here?'
Someone points past a workshop towards a gate set into a whitewashed wall. 'It's open,' he says.
'Don't want to get in trouble with the wife then, eh?' shouts someone else, obviously the comedian of the bunch.
I break free of the group and run for the gate. The sirens are coming from all over the place now and great sheets of flame burst forth from the burning building like dragons' breaths. My lungs are bursting as I fling open the gate and stumble through onto the canal path. Lucas is still there on the bridge. I run towards it, ignoring the pain, and force myself up the steps.
By the time I reach the top I have virtually no strength left, but it doesn't matter because Lucas grabs me and hauls me over to the car. The passenger door's open and I clamber inside, keeping low while he slams it behind me. Then he's in the driver's seat and pulling away into traffic, heading north up the Kingsland Road.
'You stink,' he comments as we pass through the first set of lights, swerving to avoid a fire engine screaming down the other way with all horns blaring.
'Well, that isn't really any surprise, is it?' I answer eventually, when my breathing's evened out a little and I've finished coughing. 'I don't want to sound ungrateful or anything, but what the hell were you doing setting a fire like that?'
He turns to me with a look of mild incredulity on his face. 'What the hell are you talking about?' he says. 'I didn't set any fire. I thought that was you.'