The results of the test were unpromising. By the feel of the wall, and the dull echoes from my kicks, it was made of solid concrete, two or three blocks thick. I could bust through eventually, but it would take a lot of work and more crucially time. The guard by the door would have ample opportunity to raise his weapon and fire.

Levering myself away from the wall, I started walking again, eyes flicking from the door to the wall at the front of the cell. The door looked pretty solid steel but maybe the wall it was set in wasn't as thick as the others. Perhaps I could break through it quicker than through the sides or back. Wait until it was definitely night, hope the police left me alone in the cell, then smash through and …

No. Even if the police left me, the video cameras set in the corners above the door wouldn't. Someone would be watching all the time. The alarm would sound as soon as I attacked the wall, and the corridor outside would fill with police within seconds.

It had to be the ceiling. From where I stood, I'd no idea whether it was reinforced or normal, if I could punch a way through or not. But it was the only logical escape route. If I was left alone, I could knock out the cameras, take to the rafters, and hopefully lose my pursuers along the way. I wouldn't have time to search for Harkat and Mr Crepsley, so I'd just have to hope they made it out by themselves.

It wasn't much of a plan I still hadn't figured out how I was going to get the policemen to leave; I didn't think they'd withdraw for the night to let me catch up on my beauty sleep but at least it was the beginning of one. The rest would fall into place along the way.

I hoped!

I walked for a few minutes more, then Dave asked me to sit again, and we were back to the questions. This time they came quicker than before, more urgently. I got the sense that their patience was nearing its end. Violence couldn't be far off.