Under the leadership of Detective Superintendent Hamish Campbell they gathered in offices next to Earl’s Court police station in west London The advantages and disadvantages were clear. Because the 37-year-old victim was a high-profile television celebrity there would be immediate and constant media coverage, which would help to flush out witnesses And there was a £250,000 reward. Because of her celebrity status there was also immense pressure to make an arrest, and an unhealthy interest from time-wasters.Unsurprisingly, the police felt swamped. A “three-tier” system was set up to deal with suspects and leads. Top of the list were several old boyfriends, Ms Dando’s fianc?Alan Farthing, and six people whose names were repeatedly mentioned as strong suspects over their connections and interest in the presenter. One of the first people to be investigated was a recently released mental health patient, who a doctor reported had a fixation about Ms Dando and had said he wanted to kill her.

He was ruled out after police traced him to the north of England where his wife provided an alibi.Tier two consisted of acquaintances with an interest, such as work colleagues and all the remaining previous boyfriends going as far back as the 1970s. The final, and largest group, was made up of people with an axe to grind over Ms Dando’s work on Crimewatch UK, several contract killers, obsessive letter writers and people that witnesses had named in telephone calls to the inquiry. In this category was Barry George.The other main problem for Mr Campbell and his team was the lack of a motive. The police concentrated on three areas: the obsessive stalker; the professional contract killer; and a hit by Serbs in revenge for Ms Dando making a television appeal on behalf of Kosovan refugees.After the first few weeks the team started to concentrate on eyewitness accounts, in particular a report from a traffic warden of a Range Rover and a man ­ who was sweating profusely ­ running for a bus near the scene while using a cell phone.

Six months of exhaustive work followed with 1,200 vehicles traced, 80,000 cell phone numbers checked, and 191 CCTV surveillance cameras examined. The Range Rover, it transpired, was a Cherokee Jeep but the vehicle was ruled out. The “sweating man” was also dismissed after CCTV showed he could not have been in the area when the shooting took place. Such findings set a pattern.Breakthroughs turned out to be blind alleys Take, for example, the so-called “Utility Stalker”. Police discovered that someone had telephoned Ms Dando’s household gas, electricity and water suppliers pretending to be her brother to obtain details It transpired that the caller was a freelance reporter.

Then there was the person who used a directory inquiries system on the internet to obtain her address. Police traced the inquiry to a man in Wales who had put in Ms Dando’s name by coincidence.The shooting itself threw up one potentially crucial, but yet again frustratingly ambiguous, clue ­ the casing from the bullet. Around the lip was a series of handmade indentations, which police hoped would prove a unique “signature”. After months of inquiries the best guess is that the crimping was used to hold the 9mm bullet in the barrel of either a handgun originally designed to fire blanks, or a deactivated weapon that had been activated.The killing seemed like the flawless work of a professional hitman, but closer analysis cast doubt on that theory. A contract killer would use more than one shot to ensure the victim was dead. A disguise would have been worn, a getaway vehicle in place, and surely a better firearm would have been used.

The more likely theory is that it was the work of an amateur.Teams from the Metropolitan Police examined the work done by the investigation team to make sure they hadn’t missed anything. The National Crime Faculty and outside experts were consulted. All gave Mr Campbell and the team a clean bill of health.In November 1999, the police made what was to prove and inspired decision and changed tack. Prompted by the discovery that there were 140 people who could be described as having an “unhealthy interest” or obsession with Ms Dando they concentrated on the stalker theory.Three stalkers were immediately arrested, but then dismissed from inquiries.