“It seems kind of — poky. What’s that big place down the corridor? The pool room?”

“We call it the Cabinet Room, sir.”

The political secretary returned, and escorted him up the stairs. The walls were lined with portraits of what looked like previous Prime Ministers. Henry recognized some: Churchill, Thatcher, Major, Blair, Portillo.

The Prime Minister was standing in front of the window.

Over the PM’s grey-suited shoulder was a hell of a view, of what looked like Horse Guards Parade. A couple of other people — a man and a woman, both sweating in heavy suits — were sitting in hard-backed chairs before the desk. The desk itself was a mess; its green leather top was covered by loose papers and scribbled notes and a big map of Britain. There were plates of abandoned sandwiches on the window sill, and a half-drunk bottle of red wine and three glasses leaving stains on the desk. It looked as if meetings had been going on here through the night.

The Prime Minister turned and came forward. He looked tired, his face slack, his thick hair greyer than Henry remembered from TV. “I’m Bob Fames,” he said. “Dr Meacher, thank you for coming.”

“It’s, umm, an honour.”

Fames introduced the others. The man, so fat his belly strained the buttons of his off-white shirt, was called Dave Holland, and he was the environment minister. The woman, a thin, intense Asian, was called Indira Bhide. Her title was Home Secretary, which meant, as Henry understood it, she was the most senior interior minister.

Fames said, “We have projections from our own science advisers. But Professor McDiarmid tells us you’re the best qualified to brief us on this phenomenon.”

Henry wasn’t expecting that. Was McDiarmid uncharacteristically avoiding the credit for Henry’s work on the Moonseed — or, more likely, trying to avoid the heavy shit?

“Tell us what we’re dealing with here, Dr Meacher,” Fames said. Henry spread his hands and summarized what he’d found out about the Moonseed. “It eats rock. It prefers igneous rocks — basalt, for instance. Volcanic rocks. It is spreading across surface rock, subsurface rock, and down into the mantle. Also, after the Arthur’s Seat incident, it is also spreading through the mantle itself, and through the stratosphere in the form of dust.”

“I’m told it slowed down, after the Edinburgh eruption.”

“Yes. I expected that.”

“You did?”

“It doesn’t just grow. It builds things. Structures in the rock. Now it’s into the deeper rock, we think it is busy building. But its spread will resume.”

Holland pulled his lip. “So you say.”

“Yes.”

“Not everyone agrees with you.”

He’d been expecting that. “They haven’t had time to study it the way I have.”

They were staring at him, their faces grave — Christ, they’d already lost a city, they’d already presided over Britain’s biggest peacetime disaster — but, even so, not grave enough.