Police quiz Dando fanatics

Police question passers-by outside Ms Dando's home

At least 140 people had an "unhealthy interest or obsession" with murdered television presenter Jill Dando, police have revealed.

Most have already been eliminated from the inquiry but some are still to be interviewed a year to the day of Ms Dando's death, Scotland Yard has confirmed.

Chief Inspector Hamish Campbell, who is leading the murder inquiry, said that information received in the last 10 days has shed new light on the investigation.

"There has been other information which causes me some concern that we waited a year to receive it," Mr Campbell told the BBC's Radio 4 programme.

There has been other information which causes me some concern that we waited a year to receive it.

Chief Inspector Hamish Campbell

He said there were still people who knew something about the case - relating to the gun or to suspects seen in the street - which he urged to come forward.

The lone stalker theory was, said the chief inspector, still "the most compelling argument at the moment".

A police spokeswoman added that 1,800 names had been put forward to the incident room as possible suspects.

"The more important of these suspects have been seen and eliminated from the inquiry," she said.

Ms Dando's family are marking the first anniversary of her death with a day of quiet remembrance in her home town, Weston-Super-Mare, Somerset.

One year on, police hope to jog memories

Her brother Nigel Dando said he and his father, Jack, believed the police would eventually catch the murderer.

Detectives have been at the murder scene outside Miss Dando's home in Gowan Avenue, Fulham, south west London since Tuesday.

Their fresh appeal to people living and working in the area has so far produced 31 new witnesses, a handful of whom are believed to have "relevant information".

Chief Inspector Campbell said the new witnesses showed the operation, which ends on Thursday, had already been "a very useful exercise".

Retracing steps

The 45-strong investigation team is still trawling through information from a second Crimewatch appeal, which gave police 200 new names. Twenty names are seen as "relevant and interesting".

Chief Inspector Campbell said that his officers have tried not to think about the intense pressure to catch the killer over the past 12 months.

"We can't produce results just because of the massive media interest," he said. "But I still remain confident and optimistic that we will get the solution to this appalling crime."

Ms Dando was killed on her doorstep

Further details of the investigation have been released by Scotland Yard, along with hitherto unseen CCTV footage of Ms Dando shopping on the morning of her death.

A spokeswoman confirmed that more than 4,000 people had been spoken to by police as potential witnesses or suspects and approximately 1,700 statements had been taken.

She added that almost 500 names from Ms Dando's Filofax and 13,700 e-mails received by the BBC before and after the murder are being examined.

More than 80,000 mobile phone numbers have been identified as being used near Ms Dando's home, after witness reports of a man using a mobile phone about the time of the shooting.

Obsessive fan theory

Detectives are understood to believe that Ms Dando's killer may have been an obsessive fan who secretly watched her home for several weeks before shooting her.

Another theory, apparently favoured by Ms Dando's fiancé Dr Alan Farthing, was that she was executed by a stalker who could not cope with the idea that she was soon to marry.

Officers have not ruled out the theory that she was the victim of a contract killer but no one has come forward with credible information, despite a £250,000 reward.