This was no good. He had to get back on to the roofs where the heavier and less agile guards would be at a disadvantage and he might be able to get his bearings. He saw his chance and vaulted over the edge of the walkway on to a building below. He hared across the roof, pumping his arms, taking as long strides as he could. Then he was in a gulley between two buildings, then out on to a narrow flat section, then he jumped and was in the air. He landed with a sickening rib-cracking jolt on the edge of the next roof, face down, the lower half of his body hanging over the edge.

He struggled to his hands and knees and took a deep breath. His lungs hurt like hell. Come to that, his whole body hurt like hell. He wasn’t sure he could go on.

Just ignore it.

There’s nothing broken.

There’ll just be a few more bruises to count in the morning.

He got to his feet and shook his head, but when he looked back he saw the black shapes of his pursuers, hard behind him.

He ran on.

Behind him he heard a yell and a thud followed by a short scream.

He glanced back.

There was only one guard after him now.

The other one had mistimed the jump.

Up ahead he saw a wide gap between this building and the next one. He had no idea how wide it was and didn’t have time to find out; he would just have to risk it.

He put on more speed, powering his body forward, urging his legs to work harder than they had ever done before.

He reached the edge of the roof and there was a moment of sheer terror as he realised the gap was much wider than he’d thought. Much, much wider than anything he’d ever attempted at Eton. He’d somehow doubled back on himself and had got to the big crevasse between the folds of rock. There were buildings on the other side but they were an awfully long way away.

It was too late to stop, though. He was going too fast. Instead, he sped up and launched himself across the void.

He was briefly aware of a deep black fissure beneath him as he flew towards the roof on the far side.

No…

He wasn’t going to make it. It was far too wide. It was impossible. He was dropping down below the rim of the roof. Falling into that bottomless crevasse. He flung out his arms, wildly groping in the air for something to hold on to to stop his descent. And then there was a crunch. He’d hit something.

He clung on with all his strength and wept with relief.

The guard wisely didn’t attempt the jump.