"Maybe we could wire Bob?" Shona suggests.

What? I shake my head. "What do you mean?"

"If Panin makes contact again, it would really help if you had a recording angel," she points out.

"There was a word in that sentence: if." I look at Iris for support but she's nodding thoughtfully along with Shona. "Panin's not going to make contact on working hours, and if it's all right by you, I'd rather not wear a wire during all my off-duty life. Now, if you want me to use that business card and wear a recorder while we're talking, that's another matter. But I think we ought to have something to trade with him before we go there, otherwise he's not going to give us anything for free."

"Point," says Iris.

Vikram looks at me through slitted eyes. "We should wire him anyway," he suggests maliciously, "just in case."

I sink back in my chair, racking my brain for plausible defenses. We've only been in this meeting for half an hour and already it feels like a decade: what a morning! But it could be worse: I've got to run Angleton's little errand at two o'clock . . .

10. The nightmare stacks

THERE IS A RAILWAY UNDER LONDON, BUT IT'S PROBABLY NOT the one you're thinking of.

Scratch that. There are many railways under London. There are the tube lines that everyone knows about, hundreds of kilometers, dozens of lines, carrying millions of people every day. And there are the London commuter rail lines, many of which run underground for part or all of their length. There are the other major railway links such as CrossRail and the Eurostar tunnel into St. Pancras. There's even the Docklands Light Railway, if you squint.

But these are just the currently operational lines that are open to the public. There are other lines you probably don't know about. There are the deep tube tunnels that were never opened to the public, built to serve the needs of wartime government. Some of them have been abandoned; others turned into archives and secure stores. There are the special platforms off the public tube stations, the systems built during the 1940s and 1950s to rush MPs and royalty away from the capital at an hour's notice in time of war. These are the trains of government, buried deep and half-forgotten.

And then there are the weird ones. The Necropolis railway that ran from behind Waterloo to Brookwood cemetery in Surrey, along the converted track bed of which I ran last night. The coal tunnels that distributed fuel to the power stations of South London and the buried generator halls that powered the tube network. And the MailRail narrow-gauge tunnels that for over a century hauled sacks of letters and parcels between Paddington and Whitechapel, until it was officially closed in 2003.

Closed?

Not so fast.