Focus : The Man Who Knew Too Much? : HBO FILM ABOUT THE ASSASSINATION OF THE MAN WHO MADE A ‘SUPER GUN’ POSES QUESTIONS OF REAL INTRIGUE

LONDON — Who shot Gerald Bull twice in the head outside his Brussels apartment on the morning of March 22, 1990? Why was the portly 62-year-old Canadian arms designer assassinated? Were the governments of the United States, Great Britain, Iraq, Iran, Israel or South Africa responsible?

Bull was in the process of building a “super gun” for Saddam Hussein on the eve of the Iraqi dictator’s invasion of Kuwait. The murder precipitated the biggest political scandal Britain has seen in years. The extent of U.S. involvement, if any, in Bull’s operation has not yet been disclosed.

HBO’s thriller “Doomsday Gun,” which airs Saturday, addresses this labyrinth of questions. Frank Langella stars as the mysterious weapons innovator; Alan Arkin, James Fox and Kevin Spacey co-star.

Based on information in the public record, the script is outrageous enough for Langella to say, “ ‘Doomsday Gun’ reaffirms what a pawn I am in my government. ... Americans are amazingly unsophisticated about this.

Sitting in his suite at the Athenaeum Hotel following a day of filming at Twickenham Studios, Langella talks with grim fascination about the man he plays. In 1972, Gerald Bull was granted American citizenship by a special act of Congress because of his work for NASA. He later designed weapons systems for China, Israel and South Africa.

But Bull’s real interest was in developing the world’s biggest weapon--a super gun with a barrel the length of two football fields, capable of firing a shell the size of a telephone booth 500 miles. At the height of the Iran-Iraq War, he found a patron in Hussein. Bull was so consumed by the scientific challenge that he ignored the international arms embargo against Iraq.

“To other people, Bull was a devil,” Langella says. “To me, he was a compulsive, megalomaniacal, blinkered genius. When you’re playing someone, you can’t step outside and morally judge them. Bull’s drive was to create the greatest weapon, and he paid for it with his life.”

To prepare for the role, Langella met with Bull’s second-in-command, Christopher Cowley, a consultant on the film.

“Chris and I talked for five hours. I pumped him about what Bull was like, how he felt about things. I had to find a way not to judge the man. I have little kids, and this gun will kill kids.”

On another production day, Fox stands alone, feeding the ducks, at the edge of the Serpentine, a lake in the middle of Hyde Park. An innocent Sunday outing, except that Fox’s character, a British intelligence agent, was about to rendezvous with a CIA contact (Spacey). The topic of conversation: what Bull has been up to lately.

To subvert the arms embargo, Bull had arranged to have different components of the super gun made throughout Europe. They would then be assembled on-site in Iraq. He ordered the gun barrel from a British manufacturer, describing it as an oil pipe. After Bull’s death, British customs impounded the huge metal cylinders, identifying them as gun barrels en route to Iraq.

The resulting brouhaha, which became part of a government investigation known as the Scott Inquiry in Britain, is just now concluding. British producer Michael Deakin says, “Publicly, Britain’s policy was not to provide arms to Iraq. But we were doing it, as indeed were the Americans. Bull knew it was illegal, and the British knew it was illegal, but we could keep an eye on it.

“However, customs was uninfluenced by the government. When they seized those great, huge tubes and said they were gun barrels, the prime minister’s press secretary had an off-the-record briefing saying customs have gone mad. Customs got enraged and said the government was lying and waved around copies of Bull’s book. Some very senior customs person blew the whistle, but who told customs? In the film, Kevin Spacey does, but in reality nobody knows. Maybe it was the Mossad,” Israel’s foreign intelligence agency.

So who shot Bull?

“We could make five different movies with five different reasons,” director Robert Young adds. “Bull knew a lot about a lot of people, and he had reason to be worried. He was constantly going to MI6 (Britain’s intelligence service), the CIA and Mossad, telling them what he was doing. He was helping Iraq with their Scud missiles--a dangerous pastime.

“To pursue his dream, he was feeding the jackals. Who was providing and using end-user certificates? Bull could blow the whistle. The easiest thing to do was to kill him. I don’t know who did it. I change my opinion from day to day.”

“Bull was killed because he was naive,” Fox says. ‘He didn’t realize he knew too much.”

“When we began, mine was the standard view--the Mossad,” producer Deakin says about who killed Bull. “Now, everybody thinks it was the British. Bull knew so much about what the Scott Inquiry was inquiring into.’

The Scott Inquiry actually borrowed HBO’s super gun model for one of its hearings, and was aware of the full-scale replica that HBO built in the Spanish desert out of fiberglass, cardboard and sewage pipes. “I had this fantasy that Israel would see it on their satellite and take it out,” Deakin says. That didn’t happen.

“Doomsday Gun” airs Saturday at 8 p.m. on HBO.