Tyburn looked stricken, and for a moment I felt genuinely sorry for her because none of us is ever grown-up enough that our mothers don’t think they can’t beat us. She slipped a slimline Nokia from her pocket and dialled a number without taking her eyes off mine. ‘Sylvia,’ she said. ‘Is the Commissioner available? Good. Could I have a quick word?’ Then, having made her point to her own satisfaction, she turned and walked from the room. I resisted the urge to gloat but I did glance over at Beverley to see if she was impressed with me. She gave me a studiously indifferent look that was as good as a blown kiss.

‘Peter,’ said Mama Thames, and beckoned me over to her chair. She indicated that she wanted to tell me something private. I tried to bend down with as much dignity as I could but I found myself, much to Brent’s amusement, on my knees before her. She leaned forward and brushed her lips against my forehead.

For a moment it was as if I stood high up on the middle cowling of the Thames Barrier looking east over the mouth of the river. I could feel the towers of Canary Wharf rising triumphantly at my back and beyond them the docks, the White Tower and all the bridges, bells and houses of London town. But ahead of me over the horizon I could feel the storm surge, the fatal combination of high tides, global warming and poor planning, waiting. Ready to drive a wall of water ten metres high up the river and bring down the bridges, towers and Uncle Tom Cobley and all.

‘Just so you understand,’ said Mama Thames, ‘where the real power lies.’

‘Yes, Mama,’ I said.

‘I expect you to sort out my dispute with the Old Man,’ she said.

‘I’ll do my best,’ I said.

‘Good boy,’ she said. ‘And because of your good manners, I have a last gift.’ She bent her head and whispered a name in my ear: ‘Tiberius Claudius Verica.’

The paratroopers were gone by the time I got back to Russell Square. I was back in charge of the Folly, and also responsible. Toby slammed into my ankles as soon as I was across the threshold, panting and thrashing affectionately, although once he’d established that I wasn’t carrying anything edible he lost interest and scampered off. Molly was waiting for me at the foot of the western stairs. I told her that Nightingale was conscious and then lied and said that he’d asked how she was. I told her what I was planning to do and she physically recoiled.

‘I’m just going to my room to get some stuff,’ I said. ‘I’ll be back down in half an hour.’