In the far cloister a dark bulky figure moved. Just restlessly. There was no sense of menace, but Tyler would have liked the movement to have a purpose. Suddenly uneasy, he turned back to the room.

"So… so, have we come to any conclusions?" Martin, a military historian, gave him his cue. "But British and French nuclear forces couldn't create anything like those levels of damage, could they?"

"It seems very unlikely. Mc Namara was talking about using up to 3, 400 nuclear warheads, 170, 000 kilotons total yield. I don't think we can forsee a scenario that gives Europe any such force. And. if we assume a counter-city targetting policy, and assume further that we could knock out the sixteen biggest Russian cities west of the Volga, then…" he took out the useless paper again; "… then the maximum immediate casualties we could inflict are in the region of twenty-six million. After that, the law of diminishing returns sets in because we'd be targetting on smaller and smaller towns, so a few more warheads don't help much."

"Are you including Leningrad and Moscow?" Martin asked.

"Yes. And ignoring Moscow's anti-ballistic missile defences for the moment, too. But in the Great Patriotic War-" they chuckled at the phrase but he had them with him; "-the Russians suffered, well, the figures aren't certain, but they usually claim up to twenty million. By contrast, Britain lost under half a million dead and the United States less than 300, 000 – almost none of those civilians, of course. That may throw a new light on deterrence. Perhaps Europe can threaten the Soviet Union with really no more casualties than they know they can absorb fairly comfortably. After all, they did win that war.

"So where does that leave us, gentlemen?"

They became very quiet and thoughtful. It was important that one of them suggested the answer, so he waited. He wanted to see if the dark figure was still in the cloister, but was afraid it still would be. There had been others loitering recently, he believed.

Surprisingly, it was another of the service undergraduates who spoke up. "Then we either leave nuclear affairs to the Americans, don't we, sir? – which is just about what we're doing at the moment anyway, I think – or we try to find some unacceptable damage we can inflict on Russia that isn't just measured in terms of casualties."

It was the right answer, but he waited a little longer. Another Army student gave a murmur of agreement, out of trade union solidarity. -Tyler said: "If we can't afford to cause damage in quantity, then we should try to cause damage of quality."

"That's what I meant, sir."

"It seems like a good idea."

Carefully briefed, the porter turned them out at twenty to eight. Tyler could have held the seminar in his rooms – his set was quite big enough – but then the keenest undergraduates stayed on to argue and he had either to throw them out rudely or be late into hall. This way, he had time for a leisurely drink first. A whisky mac, he thought, on an evening like this; he was getting old for the Cambridge winters. There was nothing romantic and Dickensian about winter here, just a cancerous dampness rising from the old stonework and a wind that swept in unhindered by any hill more than a thousand feet high from well beyond Moscow itself. The traditional invasion route of Northern Europe had been plotted by the east wind long before the first Mongol horde.

He took a detour to pass through the cloister opposite the Library, but it was empty. His first thought as he reached his rooms was that he shouldn't have left so many lights on, then he saw the black figure in front of the gas fire. For a moment he just stared.

"Cher Maоtre, "George Harbinger said, holding out his hand; "You do keep such a bloody cold university here. But stay, is that a bottle of spirituous liquor I see in the corner, its cap towards your hand?"

The darkness was a thick expensive overcoat, now unbuttoned and its effect rather spoiled by a soft hat that should have fishing flies in it. Tyler went quickly to the corner and poured two whiskies, skipping the plan of a whisky mac.

"Will you come into hall?" he asked.

"No thank you, no insult intended, but I think we'd do best not to advertise your connection with the seat of the almighty." George was one of the Prime Minister's private secretaries, particularly concerned with defence and security. He was in his early forties, but his Hanoverian figure and thinning fair hair made him look older.

He took a big gulp of his drink. "Sorry to intrude like this, but had you heard about Jerry Jackaman?"

Tyler felt a sudden lurch in his bowels. "No, I don't think so…"

"Well, he went and shot himself this afternoon." George sounded more irritated than anything. "I don't know why, except that Box 500 seems to have been investigating him about something, and now the Headmaster's climbing the walls at Number 10… and I'm here."

"So you are," Tyler said, very calmly. "Is there any particular reason?"

George sighed. "You did know he was very much against your appointment?"

"I had that impression."

"Was there any special reason for it, do you know?"

"I rather assumed that he didn't go along with my theories." In conversation, Tyler often ended a remark with a little chuckle, almost a grunt, as if to soften the seriousness of his deep voice.

"You don't think there was anything personal in it?"

"I never made a pass at his wife, anyway. No, I can't think of anything."

"You're quite sure?" George made his third and last try. "This is absolutely vital, I'm sure you appreciate. We really must know if there are any landmines we might step on."

"I really can't think of any. But did he leave a suicide note?"

"Why does everybody call it a suicide note! Why not a letter or even an essay? No, nothing that's been found yet. I talked to the Kent police super myself, on the phone… Oh well." George finished the rest of his drink. "We're planning to announce your appointment some time after the end of term, if that's all right with you. Then you can be out of touch if you don't want the media chasing you."

"That's very kind of you, George, but I don't really mind."

"Good. We'd rather not give an impression of secrecy. May I use your phone? – I'd like to reassure Number 10."

"Of course. Help yourself."

George dialled the familiar number and got an immediate answer. "It's gorgeous George here, me darling, can you find me the Headmaster? And see if the office wants me for anything. I'll be on the road for the next two hours… I'll hold." He turned back to Tyler. "When did you first meet Jackaman?"

"I can't remember… soon after he went over to Defence, and that would be a dozen years ago, wouldn't it? He was just one of those people who kept cropping up around the circuit, at defence seminars and Brussels and so on."

George grunted. "The moment we make the announcement – and it could leak before – you'll probably get the cads and rotters from Greyfriars prowling around. If you notice anything, let me know, will you?"

"Of course."

George suddenly lifted the hand-piece to his mouth. "Yes, it's me. I'm in Cambridge and I'm assured there's absolutely no connection at this end…"

Putting on his gown for hall, Tyler wondered why George, with his impeccable background of a landed family in the west country, Marlborough and Christ Church, always talked of the Soviet Bloc secret service in the language of the old lower middle-class schoolboy comics. Perhaps the answer was in the question: to George, the KGB, GRU, the Czech STB and all the others were lower middle-class cads and rotters.

But that didn't explain why schoolboys had ever wanted to read comics about schools. This time, he locked the door as he went out.