She decided for him. With a final squeeze, she released herself. “We’re not a couple of kids anymore.”

But that was exactly how he felt, and he wondered if he’d ever grow up. In the end, he turned away from her and headed not for the main elevators, but the emergency stairwell at the far end. He shoved the fire door open and started trotting down the flights of cold concrete stairs. It seemed strange that after all the times he’d done this, there was another pair of footsteps following.

He passed the sign for the ground floor, and kept on going into the basement, through the laundry, past all the storage areas and the patchboards for the electricity and the central heating and the pumps, into a narrow passageway that carried pipes along the ceiling low enough to make Madeleine stoop as she walked.

Petrovitch strode purposefully on toward a locked door that barred their way, and felt for the key in the depths of his bag.

“Once we’re through, watch your step. It’s a bit slippery.” He opened the door, and a hollow breath of stagnant water and dark mud stole in. “You get used to that.”

She took his hand again as she stepped out into the black space beyond, the mud sucking at her feet. “So where are we?”

“Underground car park at Hyde Park Corner.” He paused to adjust his vision, and led her splashing to where, amid a sea of rubble, scaffolding appeared to prop up one corner of the roof. It was covered in tatty blue plastic sheeting, which he drew aside for her and ushered her in.

Behind it, another piece of plastic covered the wall. He lifted it up and walked through into a rough cave that shouldn’t have been there. The sheeting fell back behind them.

He’d installed lights, and when he fastened the bulldog clip to the battery terminal, they winked on in a line that led along and down, out of sight. He’d made a tunnel, just about big enough to shuffle down when hunched over.

“Look upon my works, ye Mighty, and despair,” he quoted, in the absence of anything else to say.

Madeleine took a moment to stare in wide-eyed wonder. “You did all this?”

“Yeah.”

“How the hell did I not find out about it?”

“Because I’m very good at covering my tracks. The tunnel supports are from an over-order, the lighting rig is built from spare parts, the anti-gravity buckets I use to shift the spoil I make myself. I borrowed surveying lasers for keeping me straight and for telling me how far I’ve gone.”

Her shoulders sagged. “But I’m the head of security.”

“Were,” he corrected, and tossed a yellow construction worker’s hat to her. “You take this. I’ll just have to remember to duck.”

“You couldn’t have done all this by hand. You just couldn’t have.”

Petrovitch bent down and started along the tunnel. “Well, if it wasn’t me, maybe a wizard did it.”

11

Petrovitch crept downward, steadying his progress by holding on to the metal beams of the tunnel supports. Madeleine, rather than facing the steep incline head-first, turned around and backed down, searching the cool, damp rock and mud for any handholds that she could find.

He waited for her at the next level, where his tunnel broke through a thick brick wall.

“There’s a drop on the other side. Not far, but if you’re not ready for it…” He put his feet on the lip of the hole and jumped off into the darkness. From where he now stood, Madeleine was framed by the light behind her, crouched and uncertain.

“What is this?”

“It’s the Tyburn river.”

“I’ve never heard of it.”

“That’s the beauty of using it. No one can follow me down a river lost to memory.”

She looked longingly back at the faint string of light that ran back up to the car park. “You found out about it.”

“That’s because I’m brilliant.” He shrugged. “And I was looking for it, too. The deep underground lines are full of water and collapsing in on themselves, but rivers are supposed to be there. They fill up when it floods, and they empty when it doesn’t.”

She smelled the air. “Are you standing in shit?”

“Me? No.” Petrovitch moved his feet to either side of the thin ribbon of glassy water flowing down the center of the tunnel. “It’s a sewer, too, but hardly anyone’s been using the mains to flush their govno away for nearly a year. It’s as clean as it’s going to get.”

“And you have one—count them—one pair of socks.”

“Meh. They dry out.” He reached into his bag for the wind-up flashlight he kept there. He gave the handle a few twists, and switched the blue-white beam on. The curve of the brickwork overhead shimmered with reflections, while the walls glistened and shone. A channel was cut into the floor, and it contained the slow-moving stream of weedy-green water completely.

Madeleine lowered herself carefully into the culvert. “Go on, then. How far?” She stood up slowly, and discovered that the roof was high enough even for her.

“About five hundred meters and no surprises. They knew how to build stuff in those days.”

“And how old is this? Before I risk my neck.”

“The newer parts are a hundred and fifty, two hundred years old.”

“Newer? Terrific.”

“C’mon.” He banged his fist against the brickwork. “Second World War, the New Machine Jihad, cruise missiles. Nothing we want to do is going to bring it down.” He turned the flashlight against the run of the river. “We go up there. Doesn’t take long. Need the buckets first, though.”

Ten large buckets, battered and dirty, were stacked in two equal piles just inside the tunnel. They were heavy enough while empty; when full, they were a fearsome weight. Short lengths of thick rope were tied to each handle in turn. Madeleine went to lift both piles, while Petrovitch reached into the topmost bucket and pulled out a sphere. He flicked a switch, and the buckets clanged into the cool, damp air.

“Sure I mentioned these,” he said, and went to turn on the second set of buckets. He tied them together, and pulled them along behind him like a pair of reluctant dogs.

The one intrusion of modernity into the Victorian construction was the thin cable stapled to the glazed brick roof. It ran from the hole the entire length of their walk along the underground stream. Though there were side tunnels and places where rusted ladders led upward toward the hidden surface, the cable ran unerringly along in an unbroken line.

Then it disappeared at right-angles to the line of the river, through another dark hole made near the upper part of the wall.

Petrovitch gave the flashlight another wind, and the light pulsed in time with his efforts. “I had to make the opening above what I could expect the water level to rise to when it rained. I almost got it right, too. Last autumn was a bit of a pidaras, so I lost a week or two just bailing everything out.”

Madeleine raised herself up and peered through the gap. “I cannot picture you down here with a pickaxe and a shovel.” Her voice echoed in the space beyond.

“It’s the twenty-first century. Pickaxes are obsolete.” He threw his bag over the lip of the hole, then shoved the buckets through. They blithely drifted on until they hit something solid, then banged around until they were still.

He tried to climb up after them. His feet slithered on the tunnel side, but his left arm was proving an impediment. He let himself slide back, then edged one foot closer to the top. But he couldn’t do the splits, and he had to admit defeat.

“Need a hand?”

“May as well, since you’re here.”

She put her arms around his waist and lifted him off the floor, high enough that he could flick his legs over the edge of the hole and sit on the brickwork. She waited for him to ease himself down, then vaulted the wall in a single leap.

“What is this? ‘Everybody laugh at the cripple’ day?” Petrovitch crouched down to clip the lighting circuit in the new tunnel to the waiting battery. “Why don’t I just give the hospital a call and tell them to prepare for an amputation?”