The jury reached their verdict today unaware that Barry George is a convicted sex offender who had tried to break into Princess Diana's home in Kensington Palace.

The judge ruled that details of his arrest - in the palace grounds wearing combat gear, an SAS gas mask and armed with two knives and a 15ft coil of rope - would unfairly prejudice the jury against him.

George claimed he had merely been walking past the palace when he heard people approach and, fearing they were thugs, had hidden in the bushes. Police believe he was trying to break in and contact Diana.

He was placed on Scotland Yard's list of potential dangers to royal figures, but he was not charged over the 1983 incident and his files were destroyed as a matter of course after six years. However, when he was arrested for the Dando murder, officers searching his flat found pictures and articles about the Princess - and hundreds of other women - and her car registration.

When the Princess died in 1997 George was in the funeral crowd, having staying up all night at Westminster Abbey to ensure a prominent position. He held up a placard to his "Queen of Hearts", signed "Barry Bulsara, Freddie Mercury's cousin (RIP)".

The jury was also kept in the dark about George's 33-month sentence, also in 1983, for the attempted rape of a foreign language student he followed from Turnham Green Tube station and attacked in an Acton block of flats. He also has a conviction for indecent assault.

The jury did know about his history of stalking women and how he kept 2,597 photos he had taken of 419 women in his home. After the Dando murder 43 women reported he had harassed them. He also took photographs off the TV of presenters Fiona Foster, Emma Freud, Caron Keating and Anthea Turner.

George, a loner, married a Japanese woman, Itsuko Toide, who was five years his senior. At their 1989 wedding at Fulham register office he gave his occupation as stuntman. The marriage lasted barely five months before she fled to Japan, accusing him of assault.

His obsession with women is mixed with a cocktail of psychological disorders. At various times before his arrest he had paranoia, narcissism and Aspergers Syndrome diagnosed on top of his epilepsy. At the Old Bailey he was said to have an IQ of less than 80, which he shares with fewer than five per cent of the population. He is on the borderline between learning difficulties and mental handicap. The son of a Met special-constable, George was born in Hammersmith, the youngest of three children. His parents split up when he was young. From his early twenties his days were spent fantasising about exciting alter egos and glamorous women celebrities.

He pretended to be Freddie Mercury's cousin and adopted the names of Paul Gadd (Gary Glitter), Steve Majors (an amalgam of the character and actor in the Bionic Man) and Tom Palmer, the SAS hero. He tried to join the Territorial Army, Kensington and Chelsea gun club, and the police. All rejected him.

Most frightening, he was attracted like a magnet to good-looking women in the street, when his opening remark was often: "I know where you live."

The prosecution never put forward a concrete motive for Barry George being the killer of Jill Dando. By law they did not have to, but this lack of certainty was at the heart of the jury's decision.

The sister who stood by him

In the dark days after his conviction and when his first appeal was thrown out she renewed her efforts, urging supporters to wear a bright flower on their lapel. Her greatest ally was the fact that many people believed there was something not quite right about the case.

Ms Diskin, 52, has lived for 25 years in the village of Ballincollig, County Cork, where memories of British justice go further back even than the Birmingham Six and Guildford Four. A local administrator, she is married with three children. For the past eight years she has travelled the country to countless meetings.

Her website has been inundated with support. She has also helped with a book about the case.