Sefton looked over his shoulder and saw that the PA who’d answered the door had followed them in. Maybe Vincent wanted a witness at all times? She was standing on the threshold here, as if nervous of what had just been unveiled. Sefton stepped forward and put his hand up to the mirror. Then onto it. The glass was cold to the touch but no more than you might expect. There was nothing that said ‘London’ about its appearance or manufacture. There was no feeling of the Sight about it.

‘What does it do?’ said Quill.

Vincent looked awkwardly at him and his team. ‘I rather need to know how much you fellows know about … well…’

‘The power of London,’ said Sefton, adopting a confidence he didn’t feel. ‘Enough. Whatever you’re going to say, we’ll believe you.’

‘So, you’re police officers who know there are impossible things here?’ Vincent seemed fascinated. ‘My goodness. That must be so much help in your work. If you need to find a missing person or a suspect, you must be able to just make a gesture and…’ He made his own fumbling turn of fingers in the air.

‘You’d think,’ sighed Quill.

‘So you can’t do that?’

‘That’d be an operational matter,’ said Ross.

‘But at least you can defend yourselves against … against what we both know is out there. Please tell me you can do that.’

Ross raised her eyebrow at him. ‘And again.’

‘You were going to tell us, sir,’ said Quill, ‘what the scrying glass does.’

‘You mean you don’t know? Well, that makes this more awkward, in that I don’t see why I should…’ He trailed off, but seemed to make up his mind as Quill’s expression became darker. ‘I suppose you could find out from just about anyone in the community. Look, let me start at the beginning. I suppose it all began on the day I walked out of the Bussard Inquiry into phone hacking, having told them I’d run roughshod through my media business, found a few editors responsible for looking illicitly into the mobile phones of politicians and celebrities and sacked them all. I gave my word to those bastards – and, more importantly, to the public who buy my papers – that from now on mine was going to be the clean press corporation which didn’t do that sort of thing.’

‘How very ethical,’ said Costain, a completely non-ironic look on his face.

‘Not so much, actually,’ said Vincent. ‘I could see the way the wind was blowing – towards bloody government regulation if we weren’t careful – and I wanted to be the one who could use being spotless as a unique selling point. Trouble was … how do I put this?’

‘It’s not easy being clean?’ said Quill.