George grunted.

"Probably a Major Azarov," Agnes said. "We had him down as just a support agent, but Harry says he's a trained tearaway as well. Luckily we had our trusty flick-knife with us…"

"A flick-knife?" George said heavily. He was slightly drunk, but knew it. "A flick-knife. You didn't tell me you were taking that.

"You didn't ask."

"I didn't ask if you were taking one of the new FH-70 howitzers, either, but next time I'll have a complete list. And you really burned down that houseboat?"

"The letter might have been on board; it wasn't in the papers I'd pinched. I was just trying to stop as many rabbit-holes as I could."

"If she was going off with you," Agnes said, "it was most likely in her handbag."

"If she read thrillers," George said, "she probably left it in a sealed envelope with her solicitors and orders to send it to number 2 Dzerzhinsky Street in the event of her untimely demise. Do we know who her solicitors are?"

"I can find out tomorrow," Agnes said. "And then…" she delicately took a book of matches from her handbag and laid it on the desk beside Maxim.

"Thank you," he said politely. "But I prefer my own."

"Dear Heaven, are you two trying to give me a stroke?" George asked.›From the floor below, there came a gentle rumble of applause; somebody had just finished a speech. "And now where are we?"

"If Professor Tyler was bidding for it, we know the letter's real," Maxim said. "At best it could have been burned. At worst we know who wrote it."

"Who?"

"Robert Reginald 'Etheridge." Maxim took a notebook from his pocket. "Born 1923 in a place called Bishop Wilton near York. He was a farm boy brought up on tractors. He enlisted in 1940 and the Yorkshire Dragoons took him as a driver…"

"Whatever happened to them?" George asked instinctively, pouring more champagne all round. The room was small enough that nobody had to get up, just reach.

"The Yorkshire Dragoons were amalgamated with two other regiments to form the Queen's Own Yorkshire Yeomanry in 1956. Since then, they've been reduced to just a squadron in the Queen's Own Yeomanry."

After a while, George asked: "Did you just happen to know that?"

"I never look these things up just because you might ask."

Agnes swallowed a chuckle and choked on it.

"Go on," George said stiffly.

"He was in Egypt with their motor battalion and volunteered for the Long Range Desert Group in 1942. They accepted him with a drop from corporal to private, and the only mention of him in The Gates of the Grave is on the last patrol Tyler led in the LRDG. Etheridge was one of the three survivors. After that he was shipped home and never went abroad again. He finished the war as a sergeant driving instructor, demobbed late '45. No claim for any disability pension."

"Why d'you say that?" Agnes pounced.

"There seems to be a doubt about his mental stability. Just a hint in his records."

"Doubt?" George said. "I should have thought it was a crystal certainty. The man went to Canada voluntarily, didn't he? – and then changed his name to Bruckshaw and drank himself to death. Guilty on all three charges."

Maxim smiled politely and sipped the lukewarm champagne. He didn't much like champagne, even cold.

"You say three men survived," Agnes said. "Etheridge, Tyler himself, and…?"

"A French lieutenant, Henri de Carette. We don't have his records, of course, but it's in the book. He was a career officer, commissioned just before the war and retired as a full colonel something over ten years ago. He's still alive."

"That can't be in Tyler's book," George said suspiciously.

"I rang our military attache's office in Paris. They're going to find his address."

"God, I hope they go carefully. The French get paranoid at any hint of us playing the Great Game on their pitch. No, they'll know what they're doing… So now where does that leave us?"

Maxim shrugged.

"There's one other person who knows what's in that letter," Agnes said.

"I know that," George said. "But we can't exactly walk up to him and say, 'Excuse me Professor but what horrible thing did you get up to in the desert in early '43 that could be the subject of a letter from the late Sergeant Etheridge?' We need that man."

"What for?"

George held up the champagne bottle, stared moodily at how little was left, and poured it out. "The state provideth and the state drinketh, blessed be the name of the state. The taxpayer can always eat cake." The bottle clanged into the waste bucket. "You two can keep shut up; you wouldn't be in your jobs if you couldn't… In a couple of weeks Tyler goes to Luxembourg to talk to the French and West Germans about nuclear targetting policy. All this is rather behind the Americans' backs.

"He's the only person we've got whom the French will listen to on defence, particularly nuclear. He speaks the language well, he doesn't trust Washington, and he really seems to believe in a third world war. What more can they ask?"

"I believe in a third world war," Agnes said. "It's the fourth one I've me doubts about. But thank you for telling us this, since Greyfriars must have known long ago, the way they've stepped up their campaign on Tyler."

"They knew he was going to head the review committee; we don't know if they know about Luxembourg."

"If Bonn's involved, then they know." There had just been a new eruption of security scandals in West Germany, with lonely secretaries to important officials getting seduced by trained gigolos from East Germany. It was an old story, but to Box 500 it didn't get any better in the constant retelling.

"Maybe, maybe." There was another rumble of laughter and applause from the drawing rooms. "At least I'm missing the speechifying… So – it seems as if we'd better talk to this de Carette, once we know where he lives. I'm not farming it out to Six; Harry, can you do it, the soldier to soldier approach?"

"I can try."

"Also try not to take a flick-knife this time."

Back down in the Private Secretaries' room, George checked through the tray of paperwork that had arrived in the last two hours. Agnes sat on the edge of his desk, listening to the guests clumping down the stairs outside in seven languages.

"Would you have thought of simply burning that houseboat?" George asked.

She considered. "I hope so."

"You hope so?"

"He might have destroyed the letter, and I assume that's what we want. Especially now we know whatever it says is true."

"Yees." George made it a long, unleavened word.

"And if he hadn't had that flick-knife, he could be dead, the way he told it. I assume that's something we don't want: British Army officer attached to Number 10 found dead on Irish houseboat of woman murdered in-"

"Yes, yes, yes." George glared at a paper in his hand. "Why don't they write to the AUC? The Headmaster isn't responsible for the ice at Heathrow… You don't think Harry blew that bloody woman up himself, as well?"

"Why should he? And the funny thing is… I think he'd have told us if he had."

George let the letter drift back into the tray but went on staring at it, unseeing. Then he said quietly: "I hope you won't tell Harry, but I advised the Headmaster to pick somebody else. I think he chose Harry not because he's going somewhere in the Army, since he's quite likely not, but because he doesn't care where he's going any more. I still don't know if we did the right thing, but yes, I think he'd have told us. So who did it?"

"There was a certain Major Azarov also in the cast."

"If he lit the fuse, wouldn't that suggest that Muscovy already has the letter? They wouldn't want to kill her before they got it." George shivered. "But if they'd got the letter, what was Azarov doing on the houseboat?"

"Setting up our Major Maxim for a nice Anglo-Irish scandal? He could have tailed Harry from Limerick. He's a good soldier, but…"