I show him my warrant card and he nods. "All right. What is it you're after?"

"A file." I show him the slip of paper on which I've written down Mo's document reference. "It's new, it should have come in this morning."

"Follow me." He leads me through a door, to a lift, up four levels and along a corridor to a waiting room with a desk and half a dozen cheap powder-blue chairs: I vaguely recognize it from a previous visit. "Give me that and wait here."

I sit down and wait. Ten minutes later he's back, frowning. "Are you sure this is right?" he asks.

Annoyed, I think back. "Yes," I say. I read the number back to Mo, didn't I? "It's a new file, deposited last night."

"Well, it's not here yet." He shrugs. "It may still be waiting to be allocated a shelf, you know. That happens sometimes, if adding a new file triggers a shelf overflow."

"Oh." Mo won't be happy, I guess, but it establishes my cover. "Well, can you flag it for me when it comes in?"

"Certainly. If you can show me your card again?" I do so, and he takes a note of my name and departmental assignment. "Okay, Mr. Howard, I'll send you an email when the file comes into stock. Is that everything?"

"Yes, thanks, you've been very helpful." I smile. He turns to go. "Er, can you remind me the way out . . . ?"

He waves a hand at one of the doors. "Go down there, second door on the left, you can't miss it." Then he leaves.

THE SECOND DOOR ON THE LEFT OPENS ONTO A SMOOTH-FLOORED tunnel lined in white glazed tiles and illuminated by overhead fluorescent tubes of a kind that are sufficiently familiar that, when I reach the end of the tunnel and step through the gray metal door (which locks behind me with a muffled click) I am unsurprised to find myself in a passage between two tube platforms.

Half an hour and a change of line later, I swipe my Oyster card and surface, blinking at the afternoon sun. I pat the inside pocket where I secreted the sheaf of papers that Angleton gave me. And then I head back to my office in the New Annexe, where I very pointedly dial open my secure document safe and install those papers, then lock it and go home, secure in the knowledge of the first half of a job well done.

(Like I said: fatal accidents never happen because of just one mistake.)

11. Crime scenes

I DON'T FUNCTION WELL IN THE SMALL HOURS OF THE MORNING. I sleep like a log, and I have difficulty pulling my wits about me if something wakes me in the pre-dawn dark.