I jumped down and the wind nearly blew me over backwards as I landed. The chopper lifted off without a moment’s hesitation. In the pitch dark, and without its lights on, it had vanished into the sky within moments. The clattering of its engine and rotors faded, and suddenly Father Christmas was alone, very, very alone. The wind howled, tore at my clothes, trying to push me over to the edge.

I put down my hold-all, removed a powerful torch from it, and switched it on.

If this was the sort of thing Father Christmas had to do for a living, I decided he could keep it. The wind ripped through my clothing and through my flesh and through my bones, howling and whining against every object that protruded on the roof. I could dimly see the lights of the Empire State Building through the thickening sleet, and I could see lights of other buildings over to my right. I was utterly alone; I had never felt so alone. I was on top of the world, in the heart of a city where most people had switched out the lights and gone off to have a good time. During the next few hours, millions of excited children would be climbing into bed and waiting for a bearded man in a red robe to come clambering down their chimneys – at any rate, those that knew what a chimney was. I didn’t have a beard or a red robe, and I didn’t have any presents to bring down Deke Sleder’s chimney.

The beam of the torch found a small steel door, and I prayed that no one had tumbled Martha and prevented her from unlocking it. If I couldn’t get in through that door, I would be a dead man by morning; no one could survive the chill factor created by the wind up here for a whole night – and since I’d dismissed my sleigh, there wasn’t a wide selection of alternative routes back to the ground short of a mountaineering feat which would have qualified me to climb the north face of the Eiger with my hands tied behind my back.

I switched off my torch, pulled out my Beretta, and turned the handle. The door opened with no effort, and I relaxed, just a fraction, for the first time since I had kissed Martha goodbye that morning. I waited some moments before peering cautiously in and snapping the torch back on. I didn’t expect a welcoming party, but I didn’t want to take any chances. I shone the torch around. It was a concrete staircase, the fire escape to the roof, exactly as shown on the architect’s plans. I pulled the door shut behind me, then, holding my torch in one hand and my gun in the other, I started descending. It was bloody creepy.