It wasn’t that super, by the standards of London super-basements, being mostly swimming pool, fitness centre and wine cellar. And it wasn’t that big a pool either, since it had to fit into the narrow footprint of a terraced house – less than ten metres long and three wide. It was lit by underwater lights that cast ripples on the ceiling and pale red marble walls. The designer had probably been going for Turkish Bath but had hit Czech Porn Shoot instead.

There was a tiled space at the near edge of the pool which sported a couple of white plastic chairs, a matching round table and, redundantly, a sun lounger. A young white woman in a blue string bikini was reclining on the lounger. I recognised her face from the pictures on Olivia’s wall – Phoebe Beaumont-Jones. One of Crew Cut’s buddies, jackets unbuttoned, hands loosely held ready by their sides stood on either side of her.

Crew Cut was sitting at the table as if expecting a waiter at any minute.

‘This is unfortunate,’ he said. He still had a wicked bruise across the side of his face – it was going a nice mottled purple and must have really hurt.

I considered telling the lot of them they were under arrest, but even I’m not that stupid. Phoebe was staring at me with a fixed expression but I could see her legs trembling.

‘Hello Phoebe,’ I said. ‘How are you doing?’

She bobbed her head nervously but she couldn’t seem to open her mouth to speak.

‘Why don’t you have a seat?’ said Crew Cut. His accent was Southern-ish but not the caricature I’d heard on TV – it was the deliberately cultured accent of someone working hard to convince you they were a reasonable and civilised man. I was immediately on my guard. Well, even more on my guard, given the room full of armed men.

‘What’s your name?’ I asked.

‘Let’s not worry about that for the moment,’ said Crew Cut.

‘What should we worry about instead?’

Crew Cut tilted his head slightly.

‘I’d say we’ve managed to get ourselves into one of those unfortunate situations,’ he said, ‘where two parties that should be allies find themselves in a confrontation.’

‘Allies?’

‘We are both the heirs to Isaac Newton,’ he said. ‘A product of the same enlightenment.’

Which made them, after Lady Helena, the second lot of heirs we’d met this week. Now personally I didn’t think of myself as the great man’s heir so much as somebody who’d wandered into his house to borrow his lawnmower, but as Stephanopoulos has indicated, on more than one occasion, sometimes my cheek is inappropriate in a modern policing context.

‘Just to be clear,’ I said, ‘you’re the American wizards?’

Crew Cut shook his head slowly.

‘Specialists, son,’ he said. ‘Our job is to deal with the problems, not create new ones.’