Of course it wouldn’t come to that. They’d find some way to combat this thing, or else it would self-limit. But still, maybe somebody should be thinking about extreme contingencies.

Now, what the hell was stirring at the back of his mind?

“Blue, I’ll call you back.”

Henry—

He put the phone down.

He lay on the bed, as the light deepened, and tried to let the thought coalesce, in the recesses of his head.

An official car came to pick him up the next morning. A black Daimler, for Christ’s sake. He sank into soft leather in the back. His escort, one of the squaddies, followed him, looking even more uncomfortable.

A police escort, two outriders, took them at a brisk pace through the London traffic.

They turned off Whitehall into Downing Street, through heavy steel barriers. Henry got out of the car, in front of what was maybe the world’s most famous front door: in fact just a polished black door set in a mundane-looking terrace.

There were press ranked up on the other side of the road, behind a cordon. There was an explosion of flash bulbs, a bank of TV lights that glared despite the brightness of the day.

“Henry!” “Henry Meacher!” “What are you going to tell the Government, Dr Meacher?” “Is Britain doomed?” “This way, Henry!”

A policeman at the door saluted him. “Christ,” said Henry, unnerved. “How did they get my name? You’d think I was the Prez come to call.”

The copper, a grizzled forty-year-old who looked as if he had seen it all, just nodded, face stern and blank.

The door opened, as if automatically, and some kind of butler let him into a pretty impressive hallway. The butler was a big, balding, well-muscled guy. A plain clothes cop, no doubt.

A young suited man shook Henry’s hand. “Dr Meacher? My name’s Pearson. I’m the Prime Minister’s PPS — uh, political secretary.”

“The Prime Minister?”

“Didn’t you know you were seeing him? He’s waiting for you upstairs in his study. I’ll tell him you’re here.”

The aide ran off up the narrow staircase. Henry was left standing with the Bruce Willis butler.

It was just a smart old town house, on the surface. But Henry knew there was more to it than met the eye. For instance there were corridors that led to the other houses in the row, such as Number Eleven, the residence of the Chancellor of the Exchequer, the finance minister. So, behind the facade, this was all one big house, like the Beatles” shared home in Help!; he half-expected to see John Lennon playing a Wurlitzer come ascending from the floor.

It was hard to believe you could run a modern country from such a place, but evidently the Brits managed.

“So this is Number Ten,” he said to Bruce Willis.

“How true, sir.”