Paul McGann, who played Topliss in a1986 BBC drama, has continued to study his life along with a team of historians. And they now believe Topliss wasn't even present at the event that first thrust him into the public spotlight. Topliss specialised in impersonating military officers, to the consternation of the establishment. And he was believed to be the ringleader of a protest by British troops at a training camp at Etaples, France, just before the battle of Pass-chendaele in 1917.

"I don't think he was at Etaples," McGann says. "The units that he served with simply weren't around there at the time."

Travel documents show that Topliss was in India in 1917 and that he contracted malaria not long before the Etaples rebellion, according to the researchers on a radio documentary about his life.They believe it is hardly possible that he could have got back to Europe in time.

To some, Topliss was a debonair charmer who challenged the class system. But others see him as little more than a common criminal, confidence trickster and, ultimately, a murderer.

Born in Derbyshire in 1896 to a working-class family, he had embarked on a life of crime by the age of 11 and was regularly in trouble before enlisting in 1914 in the Royal Army Medical Corps, serving as a stretcher-bearer in Gallipoli, Mesopotamia, Greece, Egypt and India.

He took to impersonating military officers, appearing as a lieutenant, captain or major, to cross whatever social divide he wanted.

It was after the war, in 1920, that his criminal career took a fatal turn when, while sought for his mutinous activities, he was convicted in absentia of shooting dead a taxi driver in Southampton - even though an eye witness put him 25 miles away at the time.

His photograph was circulated around the UK, and newspapers carried stories about possible sightings, of which there were hundreds in different locations.

Topliss fled to Scotland and lay low in a dilapidated shepherd's bothy until his hideout was discovered. When challenged, he started shooting and seriously wounded two men, so adding attempted murder to his list of crimes.

Within a week, Topliss, who had changed back into his private's uniform, was confronted outside Plump-ton, in Cumbria, and shot dead without a word being exchanged.

Eight decades later many questions remain unanswered. Why, for instance, was he shot,rather than captured and brought to trial? "Topliss was as much a victim of the times as he was a villain," says one researcher, Drew Mullhol-land, of Glasgow Caledonian University. "Six years after the war started in 1914 the whole social class system of Britain had changed. Topliss's ability to mimic the upper classes may have meant the authorities saw him as more of a threat than he really was."

But two previously unknown occasions on which a man answering Topliss's description could have been involved in murder have also been uncovered by Mr Mul-holland and forensic archaeologist Tony Pollard.

When a policeman was shot in Acton, west London, in February 1920, a witness saw an army officer in a white mac running away from the scene. In escaping, he was bitten by a dog. Days later, Topliss went to his mother's house to treat a wound on his leg.

On another occasion, a young woman was murdered on a train to Brighton. A friend who saw her off told police that an army officer, who was never traced but who matched Topliss's description, had boarded the train at the same time.

A list of the con man's previous convictions released during the nationwide manhunt included fraud, larceny, and attempted rape.

"There's a lot he has been accused of which he wasn't involved in," says Mr Mulholland.

In death, as in life, not everything about Percy Topliss is what it appears to be.

But Paul McGann is impressed. "As long as I live," he admits, "I'll never be as good an actor as he was."