The Metropolitan Police is using new techniques to re-examine enhanced CCTV footage of a mystery man seen at Putney Bridge station in the wake of Jill Dando's murder.

This marks the first time detectives have pursued a fresh lead since the cold case was classified as inactive several years ago. The development comes 27 years after the 37-year-old BBC presenter was shot dead on her own doorstep in west London.

On the morning of 26 April 1999, Ms Dando left her partner's home in Chiswick and travelled to her house in Fulham, a property she did not visit frequently and was in the process of selling. As she went to put her keys in the lock, an unknown attacker forced her to the ground and fired a single shot into her temple.

A neighbour reported hearing a short scream, and Ms Dando's body was discovered 14 minutes later before she was pronounced dead. At the time of her death, she was one of television's most prominent newsreaders, presenting BBC Breakfast programmes, the Six O'Clock News, and co-hosting Crimewatch alongside Nick Ross to monthly audiences of 14 million.

The Metropolitan Police subsequently launched Operation Oxborough, conducting one of its largest ever murder inquiries. Detectives interviewed more than 2,500 people and examined Ms Dando's diaries and phone records to explore whether she was targeted by an ex-partner. Those lines of enquiry were closed after each man she had been in a relationship with was ruled out of the investigation.

Ten months after the killing, police arrested local man Barry George. He was charged after a forensic scientist identified a microscopic particle in his overcoat pocket believed to be firearms residue. In July 2001, Mr George was convicted by a 10-1 majority verdict at the Old Bailey and sentenced to life imprisonment.

However, that conviction was quashed at the Court of Appeal in 2007. Evidence presented at the hearing established that Mr George had an IQ of 75 and scored in the bottom one per cent for memory and executive function tests, raising doubts about his ability to carry out the attack. The firearms residue evidence was also discredited, with a Crown Prosecution Service official conceding: “We looked for any [other] show stoppers. There weren’t any.”

Mr George, who was subsequently freed and remains the only person ever tried for the murder, later remarked in a Netflix documentary: “It makes me angry that they have taken eight years of my life.”

A prominent alternative theory explored over the years involves potential retaliation from a Serbian crime gang over her work covering the Serbia-Kosovo conflict. Just 20 days before her death, Ms Dando had presented a BBC appeal that raised more than £1 million in 24 hours for refugees, at a time when British forces were conducting air strikes in Belgrade.

What we still do not know is whether the enhanced footage from Putney Bridge will provide officers with a viable suspect, or whether the identity of the shooter will remain unsolved after more than two decades.

Police are now looking to modern digital methods to extract new details from old evidence. I'll be following this one — check back for updates.