Shelford had the outdoors face of a farmer, ruddy, chubby and cheerful. "What are you doing with the mad professors, Harry? I thought you were something don't-touch-me-there in Whitehall these days?" He tapped the side of his nose conspiratorially.

"I'm just standing in as Tyler's ADC for the moment." Maxim hoped that sounded good enough.

"Nice work if you can get it. A bugger about Jenny, wasn't it?" He chattered on before Maxim could reply. "I don't know why everybody seems to think that when the cavalry gave up horses it took to tanks. It simply traded down to dogs." A small group of cavalry officers was squelching across to the grandstand, each with a perfectly groomed and disciplined golden retriever or red setter at his heels.

"At least," Shelford said, "they used to have their brains in their arses; now they're somewhere down around their knees. D'you want to know what you're going to see this afternoon? A load of balls, that's what. You need a point-target weapon for anti-tank work, not a barrage…"

His running commentary ran on as two teams from the demonstration battalion charged out from a ring of vehicles parked in the background and started assembling the competing mortars – one American, one French. The field telephone jabbered and sergeants called out fire orders – quite unnecessarily, since both teams could see their target and had known what it would be for days past.

The mortars began to fire with deep metallic chunks, setting up puffs of blue or orange smoke around a battered old Centurion tank, lopsided and half sunk in the turf 1500 metres away. The RAF and Navy spectators lifted their binoculars to watch the fall of shot; the Army looked blasй. Tyler seemed to be making polite small talk, but turning his head to watch each smoke-burst with a perfect sense of timing.

"The trouble is," Shelford said, "that tanks don't just sit there, they move. How can you correct fire?"

"It could have a tactical influence." Maxim slipped comfortably back into the argument about weapons and tactics that is as basic to army life as brown Windsor soup. "If you know that tanks could be knocked out by…"

"You've got to have terminal guidance, infra-red, laser, even magnetic…"

"But if you could just frighten off the armoured personnel carriers…"

"Mind, infra-red would only home onto a burning vehicle, a complete waste…"

"You have to choose between fragmentation and penetration."

"Dropping mines ahead of a tank, now there…"

A large man with cropped grey hair and wearing a short coat in a lumberjack tartan came up behind them. He had vivid blue eyes, a very coarse grainy skin and a bald eagle on his shoulder couldn't have made him more American. The eyes flickered from Maxim's cap badge to the crown on his shoulder to the parachute wings just below, taking in all the information going in one sweep.

He stuck out a hand. "Good afternoon, Major. I'm David Brock, Seddon Arms." Back among the parked vehicles was a heavy, unlabelled, American camper truck.

"Harry Maxim." They shook hands and Brock waved at Shelford, who said: "Hi, David."

"Anything I can tell you about our wonder weapon?"

"I'm not buying, just browsing."

"Sure, but you could be shooting, one of these days." Brock had the easy manner of a man who is always selling but always in low gear. "Tell me, was that Professor John White Tyler who came up with you?"

"That's him."

"I heard his lectures at Princeton when I was doing a graduate year. He married a girl there… I don't think it lasted. Are you baby-sitting him?"

"Just temporarily." It had been a jolt to realise that Brock, who looked a fit fifty-five year-old, must really be some ten years younger.

"Is it all right with you if I go and say hello?" Brock asked.

"Of course."

"Once the war's over, I'll try and get him to take a cup of coffee with us in the caravan. Would you join us?"

"Where he goes, I'm supposed to."

Brock smiled and trampled off to the grandstand.

"Nice guy, that," Shelford said. "But he's on a hiding to nothing here."

"What's going to happen, then?"

Shelford looked at him curiously. "I thought you'd have known already. Politics."

"Nobody tells me anything."

"I'd assumed Tyler was here just for a laying-on of hands… well, for what you're about to receive, be truly thankful. The buzz is that you're going to get the French mortar stuffed down your throat, base-plate and all."

"Is it all that much better?" *'No," Shelford said. "I just imagine this is Be-Nice-To-The-French year. But I don't know why."

Seddon Arms' camper truck was fitted out like a stateroom on a millionaire's yacht. The furniture and wall panelling were a gentle golden beech with a matt finish, the chairs and sofa covered in a baggy cream leather, the carpeting went from wall to wall. The only hint of merchandising death was in the tinted prints of early ironclads along the walls. Even with eight or nine people aboard, it didn't seem crowded.

Maxim found himself cornered by Brock's aide-de-camp, a bright young man whose glance was always wandering, looking for a glass he could refill.

"You don't seem to have the company's name on this caravan," Maxim said.

"We prefer to keep a low profile. It comes cheaper in trucks. When we put the company logo on side, we got anti-war nuts slashing the tyres and scratching up the paintwork." He grinned. "No kidding. It really happens. What are you drinking?"

"Just the coffee, thanks." It was only half past four, but Tyler and some of the others were sipping champagne from tulip glasses. The only other soldier was the lieutenant-colonel from the development unit, and he was on coffee, too.

Tyler was saying: "We just don't have your tradition of easy interchange between the academic and government worlds, that's all. In Whitehall you're still either an insider or an outsider… but at least the military look on me more as a hawk than a dove – am I right, Colonel?"

The lieutenant-colonel smiled. "They know you've been up at the sharp end, sir."

Brock had waited patiently. "But just what are you doing in your new job, Professor?"

"I'm just chairing a policy review committee." Tyler gave his deep little chuckle. "It's one of those little Whitehall cactuses that only flowers every ten years or so. The chiefs of staff don't like it, but it keeps them guessing."

"I thought," Brock said, "that you were mostly involved with nuclear strategy these days – sir."

"That's more or less true, David-" Tyler obviously remembered his one-time student; "-but one of the main functions of the review committee is to look at the whole spectrum of defence, as one and indivisible. We've always been too compartmentalised in Europe. Our military – I'm sure you'll forgive me, Colonel-" he chuckled politely at the lieutenant-colonel; "-they tend to see nuclear warfare as a civilian affair, a matter of politics and diplomacy, nothing to do with them. What I feel we have to do is just what Herman Kahn was preaching when we were at Princeton: find the spinal cord that links your antitank mortar to the intercontinental missile, and all the vertebrae in between…"

Tyler wasn't speech-making, Maxim realised. It was quite natural for him to talk like this, and just as natural for his audience to stand quiet and listen.

When he had finished, Brock took a breath to ask a well-prepared question, but the young aide beat him to it: "What was your view on our mortar then, sir?"

Brock lifted his head and flashed the boy a look as fast and sharp as a slap in the face. The aide wilted, but Tyler talked his way slowly and gently around the social blunder. The Colonel's experts would, he was sure, provide the expertise since he himself was really incompetent to judge. And in any case, it wasn't his job. The review committee was to review policy, then break it down into tasks, perhaps, and then we'd have to see… Anyway, his own experience with mortars had only been with the old Stokes-Brandt types – which showed the aide he had known about such things before some people were even born.