"Brigadier Ferguson?" he said suddenly. "It's Billy Quigley. You said only to call you when it was big. Well this couldn't be bigger. Michael Ahern and that bitch Norah Bell and some Iranian named Ali Halabi are going to try to blow up the American President tomorrow." There was a pause. "Yes, I'm supposed to be in on it. Well this is the way of it."

"Billy boy," Ahern said, "that's really naughty of you." As Quigley turned he shot him between the eyes.

Quigley went back over the desk and Ahern picked up the phone. "Are you there, Brigadier? Michael Ahern here. You'll need a new man." He replaced the receiver, turned off the office light, and turned to Norah. "Let's go, my love."

"You knew he was an informer?" she said.

"Oh, yes, I think that's why they let him out of the Maze prison early. He was serving life, remember. They must have offered him a deal."

"The dirty bastard," she said. "And now he's screwed everything up."

"Not at all," Ahern said. "You see, Norah, it's all worked out exactly as I planned." He opened the van door and handed her in. "We'll go and get a bite to eat and then I'll tell you how we're really going to hit the President."

In 1972, aware of the growing problem of terrorism, the British Prime Minister of the day ordered the setting up of a small elite intelligence unit which became known rather bitterly in intelligence circles as the Prime Minister's private army, as it owed allegiance only to that office.

Brigadier Charles Ferguson had headed the unit since its inception, had served many Prime Ministers, but had no political allegiance whatsoever. His office was on the third floor of the Ministry of Defence overlooking Horse Guards Avenue. He had been working late when Quigley's call was patched through. He was a rather untidy-looking man in a Guards tie and tweed suit and was standing looking out of his window when there was a knock at the door.

The woman who entered was in her late twenties and wore a fawn trouser suit of excellent cut and black horn-rimmed glasses that contrasted with close-cropped red hair. She could have been a top secretary or P.A. She was, in fact, a Detective Chief Inspector of Police from Special Branch at Scotland Yard borrowed by Ferguson as his assistant after the untimely death in the line of duty of her predecessor. Her name was Hannah Bernstein.

"Was there something, Brigadier?"

"You could say so. When you worked with antiterrorism at Scotland Yard, did you ever come across a Michael Ahern?"

"Irish terrorist, Orange Protestant variety. Wasn't he Red Hand of Ulster?"

"And Norah Bell?"

"Oh, yes," Hannah Bernstein said. "A very bleak prospect, that one."

"I had an informer, Billy Quigley, in deep cover. He just phoned me to say that Ahern was masterminding a plot to blow up the American President tomorrow. He'd recruited Quigley. Bell is involved and an Iranian named Ali Halabi."

"Excuse me, sir, but I know who Halabi is. He belongs to the Army of God. That's an extreme fundamentalist group very much opposed to the Israeli-Palestine accord."

"Really?" Ferguson said. "That is interesting. Even more interesting is that Quigley was shot dead while filling me in. Ahern actually had the cheek to pick up the phone and speak to me. Told me it was him. Said I'd need a new man."

"A cool bastard, sir."

"Oh, he's that all right. Anyway, notify everyone. Scotland Yard antiterrorist unit, MI Five, and security at the American Embassy. Obviously the Secret Servicemen guarding the President will have a keen interest."

"Right, sir."

She turned to the door and he said, "One more thing. I need Dillon on this."

She turned. "Dillon, sir?"

"Sean Dillon. Don't pretend you don't know who I mean."

"The only Sean Dillon I know, sir, was the most feared enforcer the IRA ever had, and if I'm right, he tried to blow up the Prime Minister and the War Cabinet in February, nineteen ninety-one during the Gulf War."

"And nearly succeeded," Ferguson said, "but he works for this Department now, Chief Inspector, so get used to it. He only recently completed a most difficult assignment on the Prime Minister's orders that saved the Royal Family considerable grief. I need Dillon, so find him. Now on your way."

Ahern had a studio flat in what had been a warehouse beside the canal in Camden. He parked the Telecom van in the garage, then took Norah up in what had been the old freight hoist. The studio was simply furnished, the wooden floor sanded and varnished, a rug here and there, two or three large sofas. The paintings on the wall were very modern.

"Nice," she said, "but it doesn't seem you."

"It isn't. I'm on a six months' lease."

He opened the drinks cabinet, found a bottle of Jameson Irish Whiskey, and poured some into two glasses. He offered her one, then opened a window and stepped out onto a small platform overlooking the canal.

"What's going on, Michael?" she said. "I mean, we don't really stand much of a chance of blowing up the President on Constitution Hill, not now."

"I never thought for a moment that I could. You should remember, Norah, that I never let my left hand know what my right is doing."

"Explain," she said.

"Because of Quigley's phone call, wherever the President goes tomorrow they'll be on tenterhooks. Now follow my reasoning. If there is an abortive explosion on his intended route to Number Ten Downing Street, everyone heaves a sigh of relief, especially if they find what's left of Halabi there."

"Go on."

"They won't expect another attempt the same day in an entirely different context."

"My God," she said. "You planned this all along, you used Quigley."

"Poor sod." Ahern brushed past her and helped himself to more whiskey. "Once they have their explosion, they'll think that's it, but it won't be. You see, tomorrow night at seven-thirty, the American President, the Prime Minister, and selected guests board the riverboat Jersey Lily at Cadogan Pier on the Chelsea Embankment for an evening of frivolity and cocktails, cruising the Thames past the Houses of Parliament, ending up at Westminster Pier. The catering is in the hands of Orsini and Co. of whom you and I are employed as waiters." He opened a drawer and took out two security cards. "My name is Harry Smith, nice and innocuous. You'll note the false moustache and horn-rimmed glasses. I'll add those later."

"Mary Hunt," Norah said. "That does sound prim. Where did you get my photo?"

"An old one I had. I got a photographer friend to touch it up and add the spectacles. They intend a cocktail party on the forward deck, weather permitting."

"What about weapons? How would we get through security?"

"Taken care of. An associate of mine was working as a crew member until yesterday. He's left two silenced Walthers wrapped in cling film at the bottom of the sand in a fire bucket in one of the men's restrooms, and that was after the security people did their checks."

"Very clever."

"I'm no kamikaze, Norah, I intend to survive this. We hit from the upper decks. With silenced weapons, he'll go down as if he's having a heart attack."

"And what happens to us?"

"The ship has an inflatable tender on a line at the stern. My associate checked it out. It has an outboard motor. In the confusion, we'll drop in and head for the other side of the river."

"As long as the confusion is confusion enough."

"Nothing's perfect in this life. Are you with me?"

"Oh, yes," she said. "To the final end, Michael, whatever comes."

"Good girl." He put an arm round her and squeezed. "Now could we go and get something to eat? I'm starving."