"Stalkers often think that their affections are being returned," said 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 had previously been stalked for four years by John Hole, a 62- year-old retired civil servant, who bombarded her with love letters and phone calls. Mr Hole stopped pursuing Ms Dando last year after the BBC sent him a warning letter. He is not under suspicion of yesterday's attack and said that he was "very sad" to hear about her death.
Dr Crown said that the behaviour of the suspected killer as he left the scene of the attack - a witness said that he walked away calmly - fitted that of a psychopathic stalking personality.He said: "He would feel no remorse at what he had done."
Dr Crown said that while it was rare for stalkers to become murderers, stalking was much more common than people realised. Stalking was about power, aggression and, to a lesser extent, sexual feeling.
"An awful lot of celebrities are being stalked. They keep it quiet so as to avoid attracting any further attention, but I see many people in my clinics including novelists," he said.
Stalking is threatening to become the epidemic of the next millennium. It is believed that over 100 people a year become stalkers by harassing, intimidating and threatening powerless victims.
Anti-stalking legislation, the Protection from Harassment Act, was introduced in June 1997 after a series of cases where the criminal courts found themselves powerless toprotect victims. The Act gives courts the power to impose restraining orders against persistent stalkers. Breaches of an order are punishable by up to five years' imprisonment.
In the last six months, over 2,500 stalking cases have been brought before the courts and 1,250 people found guilty - but only 165 jailed. Stalking victims who took part in a conference at the weekend said, however, that they felt much safer under the new law.
"Our experience shows that stalking is not just a celebrity crime," said Diana Lamplugh, director of the Suzy Lamplugh Trust, a national charity for personal safety.
"It can happen to all sorts of people, both male and female, in all walks of life. The important thing is to inform the police immediately if you suspect you are being stalked."
Research carried out in the United States last year showed that stalking was five times more common than previously thought. The study, sponsored by the US Justice Department, estimated that over one million women and 370,000 men were stalked each year.
The findings showed that 94 per cent had had to alter their lives significantly as a result, and that the average stalking lasted for just under two years.
n Jill Dando is on the cover of the current Radio Times, wearing a leather jumpsuit and standing in front of an Aston Martin, to mark the new series of Antiques Inspectors, which began on Sunday.Reuse content