Hyde Park Corner has some of the cleanest pedestrian subways in the world – this one was decorated with colourful murals depicting the Battle of Waterloo, just in case any French tourists had some doubt about whose capital they were visiting. This time I went for speed and got within two metres. But she grabbed a startled tourist, swung him around as if dancing, and threw him down in front of me. I had to break stride to jump and that gave Lesley enough time to cut right down another passage. I cornered it myself in time to see her skid left and vanish into the ticket office. I followed slower, risking a peek around the corner to avoid any sudden surprises. Hyde Park Corner has a tiny ticket office and Lesley was already through the barrier. She turned to check whether I was following and that’s when I knew I was being played.

Still, I charged the barriers to drive her down the escalators. But I didn’t follow. Instead, waving my warrant card to reassure the Underground staff, I veered right and back out into the subway. Turning my Airwave back on, I ran up the stairs and found myself at the entrance to Hyde Park. I did a three-sixty scan while waiting for the Airwave to boot up. We used to wait for our electronics to warm up, now it’s our software. But there was no sight of any of the targets.

Finally the Airwave connected and I got Nightingale.

‘It’s a feint,’ I said. ‘Lesley was trying to draw me away – which means wherever they’re going is close.’ And then I looked down Knightsbridge to where the Oriental Hotel was painted a warm orange by its spotlights.

‘It’s One Hyde Park,’ I said. ‘Tell me you have spotters there already.’

‘But of course,’ said Nightingale. ‘And I believe you may be right.’

‘What makes you say that?’

‘Reynard and our friends have just walked in the front door,’ he said.

We waited for screams, but none came. That was almost worse.

All of the apartment windows were dark and Seawoll was ninety percent sure that most of the super-rich inhabitants of One Hyde Park were either temporarily not in residence or still living abroad and waiting for property prices in London to peak.

Stephanopoulos and some uniforms in full Public Order kit had sealed off the tunnel from the Oriental Hotel, but David Carey, interviewing staff, was pretty sure at least one group had made it in before it was locked down.

‘Four IC1 males in suits,’ he reported.

‘That will be the Americans,’ said Nightingale.

There were reports of burst water mains and flooding from Sloane Street and the Serpentine. I checked my notebook – all along the course of the Westbourne, whose genius loci was otherwise known as Chelsea Thames. I called Beverley and asked if she knew where her younger sister was.