THE detective who led the inquiry into Jill Dando's murder has said her case will never be solved.

Speaking in a new BBC documentary to mark 20 years since the television presenter's shooting in Fulham, Hamish Campbell said he did not think any new suspects would ever be brought to court.

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His team arrested local man Barry George on suspicion of murder in 2000, one year after Miss Dando was killed.

Mr George, who had a history of stalking women and sexual offences, was convicted and imprisoned for eight years, then acquitted and released after a retrial in 2008.

Asked by the BBC whether he thought Jill Dando's murder would ever be solved, Mr Campbell said: "Do I think somebody will come back to court? Probably not, no."

He said: "Sometimes I felt we were a day away from solving it and other times, I thought 'no, we're a long way away'.

"Senior officers were asking 'what are the likelihoods of this case being resolved?'

"We had over 2,000 people named as potential suspects or responsible. Some actions to trace and eliminate one person might take a day. One action might take two weeks.

"But there's thousands of them and that's the issue of managing stranger homicides."

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The 37-year-old television personality, best known for presenting BBC Crimewatch, was killed by a single gunshot to the head as she stood on the doorstep of her home on April 26 1999.

She had just arrived back at the address after staying with her fiance, consultant gynaecologist Dr Alan Farthing, whom she had be due to wed in September that year.  

The new documentary reveals the decision-making happening behind the scenes of the inquiry into Miss Dando's murder.

It will show how a particle of gunshot residue in the pocket of a coat police found in Barry George's house became the key forensic evidence against him.

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In his retrial, the jury accepted that one particle of gunshot residue was insufficient forensic evidence to place him at the scene of the murder.

The film will also show how BBC director general Tony Hall, then Head of News at the BBC, was targeted with threatening phone calls in the weeks after Jill Dando's murder.

"We had three calls, as I recall, to the BBC switchboards in London and Belfast," he said.

"I listened to the voice of one of them, which said basically, I was next.

"I mean they were threatening me.

"I have no idea what that amounted to, Was it a real threat? Was it not a threat?

"You know there are often copycat things that happen after these sorts of events, and the police took it seriously, but I don't know."

The Murder of Jill Dando will air on BBC One at 9pm on Tuesday April 2.