Why did they think, or how did they know? I must find out.

Perhaps he would tell me, the short, squat-bodied Chinese who was walking behind me on the bright curved surface of the copper samovar, fifty paces, I would have said, behind me, allowing for the reduction in size of everything reflected there, a cup of tea, how nice, but I haven't the time just now, warming their hands, the little group around the stall, warming their hands on the cups as the tea came gushing from the spout, hanging back a little now, he was hanging back, because here the street was clearer and if I looked around he'd stand out and I might notice him, he was good at the rudiments of urban tracking and that made things safer by a degree because a trained tag is predictable and his movements would be unsurprising, I could do with that.

I could do with anything in point of fact that I could get in the way of advantages, because he would carry what those Americans so delightfully call a 'piece' and it would be heavy-calibre, big enough to drop me from a distance if I looked like getting away. It was probable too that he'd been here on the roof of the world a bit longer than I had and had got used to the atmospheric pressure and would be able to run more effectively, to outrun me if I had to, through the leaden light of the forenoon.

There's a case to be made for calling us cocky, you must understand, we the brave soldiery of the thrice-accursed Sacred Bull that runs us across the board like pawns until at last the paint wears thin and the glue cracks and the head comes off and they throw us away, for calling us cocky, yes, as we work our way through the labyrinth, meeting so often face to face with our grinning fate that we lose much of our fear and become irrational in the heat of crisis, and this, my good friend, was a crisis, because the executive had moved deliberately into the surveillance field of the opposition and attracted its attention and the opposition was not some maverick terrorist cell with no claim to expertise or efficiency but the multifaceted and highly competent intelligence service of the People's Republic of China, and as I walked across the packed dirt of the next street to my right my feet felt sticky on the web.

He was keeping pace, moving across the window of a bathhouse, neat in his parka, his head turned to the side a little in case I looked back, cocky, yes, in a crisis, and this had often been our undoing, the head comes off, you understand, and they throw us away; but this was a two-edged thing, because if we couldn't allow ourselves the choice of deadly options and face the matter head-on we'd never get anywhere, would we, all we'd do is sit there in the park with a drip on our nose and a plaid rug on our knees feeding the bloody pigeons, turned again, I turned again, working my way to the edge of town through the leaden light of the forenoon.

There'd been no other choice, let's face it. That improvident diabetic up there in the monastery, that crass idiot, the messiah, my precious protege, needed the stuff in my pocket before he slipped into a coma, and I couldn't have asked Pepperidge for help because the director in the field can have no part of the action; his job is to hole up in his ivory tower and liaise with London, report to the signals board on the progress of the mission and request instructions, to protect, nurture, and advise his executive certainly, but not on the streets, in harm's way, because if a wheel comes off he provides a kind of black box for the Bureau, slipping away from the field and leaving the blood and the smoke behind him and taking a plane for Londinium and a debriefing room, there to explain what happened, why we crashed, so that our little mistakes can go down in the records and those poor little buggers in training at Norfolk can be duly warned: Here is a case, you see, where the executive began believing himself to be invulnerable, and overestimated his talents. Got cocky, yes.

Yet it was logic that drove me through these streets and I won't have it otherwise: that man had to have his medication and there was no one else who could get it for him — I'd already put that monk in hazard without meaning to — and there'd been no way I could have bought it in time without walking straight into the trap, won't have it otherwise, I tell you, I don't care what you think.

Things were not, though, going to be pretty.

I was walking a bit faster now, giving him the picture, glancing around sometimes to see if anyone was watching, my steps more purposeful, man with a mission, yea, verily, huge black yak coming the other way, pulling a cartload of dried dung, whites of his eyes, breath clouding on the air, one hoof split and bound with a metal ring, the driver chanting, head lifted to the sky, lost in his own world. I could have run now, using the yak and the cart for cover and taking whatever doorway or alley I could find, running flat out and gaining enough ground to get me clear before he could catch up; but there'd be no future in that: he could have dropped me with a shot or cut across the terrain and intercepted me, his lungs better than mine, more used to the altitude, and in any case it would only have confirmed to his agency that they were right: Xingyu Baibing was indeed in Lhasa and must now be hunted down.

Also I had a rendezvous.

Walls of a temple garden, huge cracks in it, weeds growing, a pair of timbered gates, one hanging from a rusty hinge, the other decorated with dried leaves in an intricate design, embodying prayer, presumably, or homage to the Lord Buddha, so I went in there, it seemed appropriate, went in there to keep the rendezvous.

It was mostly a ruin.

The main doors had been chained at some time but one of the hasps had been jimmied away from the woodwork and now the doors hung open. Human excrement on the worn stone steps, pages torn from a pulp magazine, a cracked boot lying on its side in a corner and the white bones of a skeleton glowing in the half-light inside the doorway, a dog's, with one leg missing.

Smell of stale incense, or perhaps a fire, a torching of aromatic timber: this could be one of a hundred temples ransacked and ravaged by the angels of Chairman Mao. It was cold in here, silent, smelling of a grave, with feeble light from the aureoles along the gallery pooling on the floor, playing on dead leaves and the carcass of a rat.

Suddenly a face in front of mine as I moved into the shadows, the shock hitting the nerves and the adrenaline hot in the blood, a face with the gold leaf peeling away from the dry cracked wood underneath, the eye sockets brooding in meditation, the hands folded across the gross belly two inches below the navel, I didn't stop, didn't hesitate, because the scenario required confidence here: I was meant to know my way, I was bringing the insulin to Dr Xingyu Baibing, for it was here that he was hidden.

Scream of a bird and the echoes played it back from the domed ceiling, a flurry of wings and a spattering and then silence again until I moved forward, my boots grating across the chipped tiles, there was a door here.

I pushed it open and it swung back, hitting the wall before I could stop it, darkness now, blindness across the eyes, and a silence so deep that even my breath echoed until I controlled it and went forward again, swinging the door shut but not with a bang, because any noise in this place could attract attention and we wouldn't want that, Dr Xingyu Baibing and I.

'I've got it,' I said, we must not ham it, must not actually say insulin.

'You were late,' at the back of the throat. 'I need it now.'

Then I waited against the wall behind the door.

I was relying on his pride.

This was a kind of inner chamber, I suppose, but it might have another door, to the outside, either locked or chained or able to be opened. There could be fixtures in here, lamps, candle sconces, Buddhas, perhaps, unless they'd been saved from the torching; by the acoustics it was a small place with a flat ceiling, not domed; there was not a photon of light here. It smelled of damp rot, with a mortuary sharpness that caught at the throat: there might be a cadaver here, neither rat's nor dog's this time, and not bared to the bone, the flesh still stirring to the feast of maggots, but we are being morbid, perhaps, the nerves producing a little video show for the imagination to work on, worried now, I was worried because I was relying on his pride and that could be a mistake.