The programme-makers re-opened the investigation into his death and found conclusive evidence to suggest that Rasputin was murdered in St Petersburg in 1916 in a plot hatched by rogue members of the British Secret Service – with a fatal shot fired at close range by Secret Agent Oswald Rayner.

The documentary is based on extraordinary new evidence uncovered by intelligence historian, and programme consultant, Andrew Cook.

In addition, BBC Timewatch brought in Richard Cullen, former Metropolitan Police Commander, and a trainer of police cadets in forensic detective work in Russia, to re open the case.

Re-examining the original autopsy reports, Richard Cullen found that the original explanation for Rasputin’s death did not tally with the forensic evidence.

In particular, he questions one of the key autopsy photographs which shows a gunshot wound situated in the centre of Rasputin’s forehead, which bears the hallmarks of a professional assassination.

The accepted version of Rasputin’s death states that he was poisoned, then shot, and finally drowned in the River Nevka by five disaffected aristocrats, led by Prince Felix Yusupov.

The conspirators were said to be concerned about Rasputin’s influence on Tsar Nicholas II, and his wife Tsarina Alexandra.

Over the years historians have questioned Yusupov’s version of events but failed to come up with credible alternative theories.