Britain's first clinic for stalkers is launched today, aiming to prevent rapes, sexual assaults and murders that result from what doctors describe as "psychological terrorism".
Millions of people suffer the unwanted attention of stalkers, often following a failed relationship. It involves their being bombarded with phone calls, texts or emails, being approached or followed or being impersonated to order or cancel goods and services.
One in five women and one in 10 men has been a victim at some stage, according to the British Crime Survey.
In the worst cases it can lead to horrific violence. Three in four women killed by their former partners had been pestered beforehand, a study has shown. The crime is sometimes referred to as "murder in slow motion".
Frank Farnham, a consultant forensic psychiatrist and joint founder of the clinic – based at St Ann's Hospital in Haringey, north London and run by Barnet, Enfield and Haringey Mental Health Trust – said there were four categories of stalker.
One group was "rejected and resentful" and wanted to get back into a relationship or destroy the other person.
A second was "incompetent suitors" who needed help as they were slightly autistic. A third was "pathologically infatuated" who had delusions of love, while the fourth was "predatory", who planned an attack and were often found with ropes and handcuffs.
Dr Farnham said: "If we can treat stalkers we can save lives. There is a great need for a co-ordinated national service that can provide specialist advice and treatment."
Offenders had not been treated in the past, except on an ad hoc basis if they had associated mental health problems, he said. But there was evidence they could be helped with drugs, such as anti-depressants, cognitive behavioural therapy and social skills training.
Katie Summers, 24, was stabbed to death in her home in 2008 by her ex-partner Brian Taylor, 29, who grew jealous after their relationship ended. Police had previously been called to the home in Farnworth, near Bolton, 11 times. Taylor was jailed for life in 2009.
The clinic is backed by the Home Office and police. Assistant Chief Constable Garry Shewan said: "Stalking steals lives."