London, Sept. 19: Rasputin, the Russian monk who became the confidant of Alexandra, the Tsarina, and her husband, Tsar Nicholas II, was killed by a British agent, according to a documentary to be broadcast next month.

An investigation into his death in 1916 has concluded that he was murdered not as had been supposed by disaffected Russian aristocrats but by Oswald Rayner, a member of the Secret Intelligence Bureau, who was working at the Russian court in St. Petersburg.

Richard Cullen, a retired Scotland Yard commander studying the case with Andrew Cook, an intelligence historian, says a new forensic analysis and an examination of official records helped him reach his conclusion.

?I am 99.9 per cent certain of this,? said Cullen, whose findings will be broadcast in the BBC2 Timewatch programme on October 1. ?There is a fair weight of evidence to show that Rayner was the man. We have conclusive proof that the previously accepted versions of events are fabrications.?

Rasputin claimed to have ?mystical powers?, which gained him the confidences of first Alexandra ? who thought that he could cure her haemophiliac son ? and Nicholas. But he was highly unpopular among the courtiers.

Now it is claimed that the bureau wanted to kill Rasputin, who was hoping to broker peace between Russia and Germany, because of his influence over the Tsar. The fear, according to Cullen, was if such a deal had been agreed in 1916, 350,000 German troops would have been freed to fight the Allies on the Western Front.

According to Timewatch, Rayner was known to be in St. Petersburg in December 1916 when Rasputin died. A close friend from university was Prince Felix Yusupov, at whose palace the murder took place.

Yusupov claimed a prominent role in the death. In his account, until now the accepted version of events, he lured Rasputin to his palace and fed him cyanide-laced cakes. When these did not take effect, he got a gun from the study where his co-conspirators waited, and fired at the monk?s heart.

He returned to the murder scene an hour later and was horrified to discover that Rasputin was still alive. The monk leapt to his feet, attacked Yusupov, then fled into the courtyard where he was gunned down by another conspirator, Vladimir Purishkevich. Yusupov wrote that the next day he dined with Rayner, who ?knew of our conspiracy and had come in search of news?.

The BBC documentary says modern forensic evidence contradicts this account. Post-mortem photographs of Rasputin show a mysterious third bullet wound in the centre of his forehead. The precise positioning of this, the fatal shot, suggests that it was the work of a professional killer.

If Rayner was the killer he never spoke about it. He burnt all his papers and took the secret to his grave in 1961. He left Russia before the end of the war and in 1920 worked for The Daily Telegraph as Finnish correspondent.