I’ve stood in the presence of Father Thames and felt his influence wash over me like an incoming tide. I’ve seen a lesser river goddess send a wall of water from one end of Covent Garden market to the other. That’s sixty tonnes of water over a distance of thirty metres – that’s a lot of power, at least 70 megawatts – about what you get from a jet engine at full throttle. And I nearly kissed her just after she’d done it too – makes you think, doesn’t it?

We know that power has to come from somewhere, and Polidori’s theories were as good as anyone else’s. But sticking a Latin tag on a theory doesn’t make it true. Not true in a way that matters.

If there had been some kind of supernatural activity, I would at least have expected to get something off the door, or the concrete of the foundations, both of which stayed stubbornly neutral. Absence of evidence, as any good archaeologist will tell you, is not the same as evidence of absence – I made a note to ask Nightingale about how things went in the countryside.

‘What’re you looking for?’ asked Stan.

‘I was looking to see if there are any tracks,’ I said.

‘There aren’t any tracks,’ said Stan. ‘If there’d been any tracks I’d have seen them.’

‘Stan’s good with tracks,’ said Dominic.

The sun had got high enough to shine directly onto the back of my neck.

‘So, no tracks?’

‘Nothing,’ said Stan.

‘So why did you think a pony did it?’

‘Don’t know,’ said Stan. ‘That was just the first thing that came into my head when I found it open.’

We were all silent for a moment – something high- pitched yodelled out amongst the trees. The heat seemed to grow around us. I realised that my bottle of water was still in the Nissan.

‘To recap,’ I said. ‘Your stash is gone but the kids are not stuck down there. It must have been people not animals. But they didn’t leave any tracks.’

‘I thought it might be aliens,’ said Stan. ‘Because there’s no tracks.’ She made a motion with her arm – like a claw dangling down.

‘Let’s hope their saucer runs on diesel, then,’ said Dominic. ‘Otherwise I think they’re going to be a bit disappointed.’

I used an app on my phone to get a GPS fix on our location and then I suggested that we head back to the Nissan before calling it in.

‘How are we going to explain what we were doing here?’ asked Dominic as he crawled back out of the rhododendrons. I said he could blame it on me doing my due diligence. ‘I thought that was the plan.’

Dominic admitted that this was true, but still wanted to know what I was going to say.