Police sources were reported as saying they believed a professional killer was responsible, and speculation immediately centred on whether the killer may have borne a grudge as a result of Ms Dando's work with the Crimewatch television programme. It was a motive police had ruled out earlier in the day.
While there was no official confirmation of the line of inquiry, the disclosure of the results of the post-mortem examination raised the possibility of a contract killing. While anyone can get hold of a knife, access to handguns - banned by the Government in response to the Dunblane massacre - is much stricter. Such weapons are now largely confined to the underworld.
The fact that Ms Dando's neighbours in Fulham, including her next-door neighbour who discovered her body, did not hear a gun shot suggests the killer used a silencer or else muffled the noise of the shot with a cushion.
It was also pointed out that the manner of the shooting suggested it was performed by someone with a degree of expertise.
Doorstep assassination with a single bullet to the back of the head is a favoured method for professional killers. Witnesses said Ms Dando often returned to her home shortly before noon, which may indicate that the attack was carefully planned.
Speculation about the motive also turned on the fact that Ms Dando may have been killed by an obsessive stalker, although such people are far less likely to have access to firearms.
Ms Dando had already been the victim of a stalker, and experts said that if such a person was responsible her planned wedding this autumn was probably the catalyst. "Stalkers are often deluded and think that their affections are being returned," said Dr Sidney Crown, a consulting psychotherapist at the Royal London Hospital.
"If they feel that the person of their affections is being disloyal, by getting married to someone else, then they are more likely to become violent."
Ms Dando was stalked for four years by John Hole, a 62-year-old retired civil servant, who bombarded her with Valentine's cards, love letters and telephone calls. He ended his pursuit after the BBC sent him a warning letter. He is not under suspicion for yesterday's attack and said he was "very sad" to hear about her death.
It is believed that over 100 people a year become stalkers by harassing, intimidating, and threatening mostly powerless victims. In Britain, up to 5,000 people are thought to have become the target of a stalker in the past 12 months.
Anti-stalking legislation, the Protection from Harassment Act, was introduced in June 1997 after a string of cases in which criminal courts found themselves powerless to protect victims.
The Act gives courts the power to impose restraining orders against persistent stalking offenders, and breaches are punishable by a maximum of five years' imprisonment. In the last six months, more than 2,500 cases have been brought before the courts, with 1,250 people found guilty - but only 165 given a custodial sentence.