Everage wilted for a moment in the face of the CDS’s vehemence. Then, ever the politician, he drew a deep breath, ready again to argue his corner.

“I said, enough,” the Prime Minister snapped. “Point taken, CDS . . . How will the Russians react?”

“That’s easy,” replied Kydd. “They’ll threaten to nuke us. For starters, they’ve got Iskander tactical nukes deployed in Kaliningrad.”

“But haven’t they’ve only got limited range and impact?” countered Little.

“Range, yes. Impact, no. Each one of those tactical nukes is many, many times more powerful than the bombs that flattened Hiroshima and Nagasaki. And you may think that is an acceptable risk sitting out of Iskander range in London,” Kydd gave both men a hard look. “But if you’re Polish, German or Danish, and well within Iskander range, you’d take a very different view. Besides, once tactical nukes start getting flung about, it’s a very short step to an exchange of intercontinental ballistic missiles . . . the really big boys. And then it’s welcome to Armageddon.”

“But surely, even if we’re outmatched conventionally, we’ve still got Trident?”

“OK, Prime Minister,” sighed Kydd, “let me take you through this from first principles. You ask what the Russians will do and I’ll repeat. They’ll do what they’ve done at the end of every snap exercise they’ve called recently. Launch an Iskander tactical nuke as what they call a de-escalatory measure to stop us dead in our tracks and stop us counter-attacking.”

“Hardly sounds to me like de-escalation. Surely them firing a nuke will lead to all-out nuclear war?” asked Little.

“That’s precisely the point, Prime Minister. It’s counter-intuitive . . . the President knows that there’s no way you are going to risk the destruction of human life in the UK by launching a Trident at Russia in response to his tactical nuke when, by so doing, you can almost guarantee a retaliatory strike from an intercontinental ballistic missile in return.”

“So, how should we respond? We just have to take it on the chin?”

“Sadly, with the state of our Armed Forces as they are today . . . Yes. That would be my advice. Plenty of people told the last government that to be effective, deterrence needs to be matched at every level, conventional and nuclear. As I’ve just explained, you can’t weaken conventional forces and expect Trident alone to protect you. Conversely, if we did have strong conventional forces, but no Trident, they could easily defeat us by threatening to nuke us and we would have no way of deterring them. By allowing our conventional forces to be run down as they have, our whole defense posture is now dangerously out of balance. When you’re up against a ruthless predatory bastard like the President, that means we are now in a very dangerous place.”

“So those billions spent on Trident were a false insurance policy, CDS?”