"Who are you really working for?"

The question knocked Farthing off balance. "What… what d'you mean?"

"You throw a grenade in the door of Number 10 – that isn't exactly a patriotic thing, is it? You say our defence is being loused up, but not how or by whom. Just whose side are you on?"

"D'you have to ask that?"

"With you, obviously yes."

"Jesus! Well, you go back and tell your bosses that the professor isn't going to… oh no. You slimy rotten sod. Just tell them.. I'll say it all. I'll say it."

He threw down the cigarette and stamped on it. The floor around his feet was a mess of ash and crushed butts. Others had made their mute protests by scratching names and rude words on the paint of the door.

Maxim waited, but it was over. He pressed the buzzer by the lavatory.

"He means Professor John White Tyler, of course," George said. "It's quite ridiculous. He's probably our best theorist on defence since the war – have you read any of his books?"

Maxim nodded.

"Well… but he's never had any direct influence until he joined the policy review committee a few weeks ago. Ridiculous."

"What about somebody getting killed?"

"He didn't say any names?" But George had hesitated just a moment and Maxim knew he was dodging something. They were sitting in the bleak neon-lit charge room just before the cells corridor. The Chief Inspector had instinctively placed himself behind the desk, leaving Maxim and George in front about to be warned that anything they said would be taken down in writing…

"No names," Maxim said. Was George a little relieved?

"Well, I don't see how we can follow that up until he does say something. D'you think he's barmy?"

Maxim glanced at the Chief, who left the question to him. "I think that's the word I'd use. He's been out of work some time, his marriage is on the rocks, he's about broke… I don't know what it adds up to medically, but if he were in my company I'd make sure he stayed back and loaded blankets into trucks rather than let him near a weapon."

The Chief smiled his skull smile. "He's not too bad with a hand grenade."

"So now," George said, "he's going to stand up in court and spout a lot of rubbish with absolute privilege, no libel suits, and muddy the water properly. How long can you delay the case?"

The Chief thought carefully. "Do you think we ought to hit him with something more than just creating a disturbance?"

"What have you got on the menu?"

The Chief opened a file on the desk. "This is something fairly new, from the Criminal Justice Act 1977. 'A person who places any article in any place whatsoever, with the intention of inducing in another a belief that it is likely to explode…' " He looked up. "Fits him like a glove, doesn't it, sir? Up to three months on summary conviction."

"Well, how long can you wait?"

"He'll get bail, of course, even if we opposed it. After that, the magistrates won't be in any rush. I'd say five weeks, give or take."

"It's the best we can do, I suppose."

"There's just one thing," the Chief said. "The suit our friend is wearing. He was properly searched when we got him in – the suit was made in Canada. Montreal. I don't know if that means anything, sir."

They dodged through the Grand Prix of Whitehall traffic and into the backwater of Downing Street. George walked with his shoulders hunched against the wind, a petulant frown on his face. The inevitable little group of tourists goggled at them as the policeman nodded to George and had the door opened immediately. The stares still embarrassed Maxim: he always felt a fraud for not being somebody important.

Once inside, George muttered: "We are going to turn that bastard inside out. I want a witness to every breath he ever drew." He glanced at Maxim.

"I told you I'm not a detective."

"I know. This isn't a one-man job, anyway. It isn't a police job, if we've got to back-track him to Canada… You haven't met Agnes Algar, have you? I'll get her over."

The ladies' annex of that particular club was being redecorated, so for a few weeks women were allowed into what was called the Library, although there was no sign that anybody ever dared touch the leather-bound books lining the walls.

George introduced them. "Major Harry Maxim – you probably know more about him than I do anyway. Miss Agnes Algar from Box 500, Five, whatever you care to call it."

"It's nice to meet a real professional," Maxim said tactfully.

"Thank you, kind sir." Agnes was about Maxim's own age, with an oval face that could be called 'friendly' and looked as if it should have freckles. She had blue eyes, a snub nose and light ginger hair cut straight but in no definable style. She wore a skirt, blouse and jacket in light brown and oatmeal shades, which most women were wearing that season. Being friendly and unmemorable was an important part of her work.

They sat on huge studded leather chairs in a corner of the room, which was long and tall enough for them to speak normally without being overheard. Agnes kept a hopeful smile on her face as she studied the man whom the intelligence community was already calling the Unknown Soldier. She had foolishly believed that, after fourteen years of security work, she knew every stupidity that Downing Street could get up to in that field. She had been wrong. They had brought in a soldier, an infantryman, no matter what he might have learned in the SAS and the Ashford course. Presumably he was a crack shot and a born leader who could crawl invisibly across a thousand miles of desert, if that was any help in Whitehall traffic, but probably he knew as much about real security work as she did about the mating habits of the giant squid.

But he will pass, all things pass, particularly soldiers when their brief postings are up. Until then, she could live with it. Agnes had that most valuable of all talents in the intelligence world, something the MI5 headhunter at Oxford had hoped for but could only guess at all those years ago: loyalty that lasted beyond disillusionment.

"Does this meeting mean that we have found favour again in the eyes of the All Highest?" she asked. She had a gentle, controlled voice, more Oxford than shire.

"You have most certainly not. There are standing orders to set the dogs on any of your calling who sets foot within a quarter mile of Number 10."

Agnes could live with that, too. Prime Ministers also passed, even if each new one was just as paranoid about the security service as the last.

"All we want-" then George caught the eye of an elderly steward. "What will you drink?"

"Ow, a small tonic wiv a large gin, pleeze, duckie." Around George, Agnes often slumped into a stage cockney accent, originally intended to embarrass him, now just a habit. Maxim and George both asked for whisky and water. The steward crumbled away towards the service door.

"All we want," George went on, "is for your mob to dig up everything they can about this Farthing person without triggering off any nuclear disasters or Questions in the House."

Agnes kept her friendly smile and fumbled in a shoulder bag shaped like a pony express pouch until she found a notebook. "I looked up his file at the Registry."

"Was he positively vetted?"

"No, just the standard procedures when he got into armaments, and topped up from time to time. He never got above junior management and he wasn't in anything really sensitive. He was… born in York. No university, just Sheffield Polytechnic. Engineering, he did quite well. National Service in the Royal Tank Regiment-" George, ex-cavalry, gave a small grunt, just as Maxim had expected. Agnes ploughed on; "-became a corporal, then he was a management trainee at BSA, he got married in…" It was a drab, dull list of facts that got fewer and less important as Farthing grew older, until, with a cutback in defence spending, his last employer dumped him on the street.