I wrapped the phone tightly in a plastic bag I’d found in the glovebox of the stolen Lada and buried it deep inside my jacket with my Russian passport and the photograph of my mother. I restarted the engine and pushed the gearstick into first. But as my foot hovered over the gas pedal, I heard my own voice come back to me.

Forget London. We’ll go east, deep into the forest. Not even your angel will be able to find us.

I didn’t have to make a run for the border. Turn east, and I could disappear – for ever, if I liked. I put my foot back on the brake and thought about that. I was beyond orders. No one could compel me to do anything. I’d been on the run for days. And now, finally, came the chance – perhaps the final chance – to escape.

But Rachel’s angel was real all right, and I knew I’d never shake it off in the trees. No matter how deep I went, the damned thing would be on my tail until the day it finally caught up with me. I could outrun any man sent to hunt me. But not even riding the fastest horse east from Arkhangel could I escape my fate.

It would be disastrous if the Russians intercepted the phone and the photograph of Rachel’s calculations. But destroying her Destroyer wouldn’t solve anything. Eventually another mind, perhaps even more brilliant – and more unhinged – than Rachel’s, would rediscover what had been lost. And then we would be at their mercy, enslaved to the interests of some unforeseen tyranny.

No. Getting out of Russia wasn’t merely a case of ensuring my own survival, or even of sabotaging the Russians. I had to stick with the plan, and make certain that what Rachel had brought into being was either used for the greater good – or never used at all – and I could only guarantee that from London. Rachel had been blinded by the brilliance of her creation, warped into madness by the power of it. Perhaps I would be, too. Perhaps Arkhangel’s promise of absolute authority would always prove impossible to protect against.

But there was someone I trusted to see clearly enough to navigate the landscape that Rachel’s angel would reform – and yet Baaz had only one part of the algorithm. Without the photograph of the writing on the wall neither of us could unlock the secrets that had driven Rachel to her death.

It didn’t matter whose side Commander Frank Knight was on. Good or bad, he was just one man – and Grumpy Jock would make sure I got to Blighty in one piece. But only by returning would I ever know why I’d been sent out in the first place. The death knell might have sounded, but this watchman was still alive.

I hit the gas, and turned west.