The killer evaded a security operation by armed police that had been set up after an incident on the estate two weeks ago. The house where the woman died had subsequently been equipped with a 'panic alarm'.
Detectives are investigating the theory that Karen Reed died in a political killing and that the target was her sister, whose husband is serving a double life-sentence for murdering the premier of the self-proclaimed Chechen republic, part of the former Soviet Union, and the leader's brother.
Mrs Reed, 33, who shared the large detached house on the town's Barnesbury Farm estate with her younger sister, Alison Ponting, died on Saturday night in a hail of bullets fired from a pistol when she opened the door to a caller.
The police believe they foiled a murder attempt two weeks ago when a patrol car followed a car on the estate and found a pistol and a marked map in the vehicle after the driver fled on foot.
Surrey police then set up armed patrols and installed high-technology alarm equipment in at least five nearby homes, including that of Mrs Reed. They warned householders not to open their doors to strangers.
Detectives believe that Mrs Reed, who is estranged from her husband Julian, failed to heed the advice after the gunman had managed to slip past police who were on patrol at the time of the shooting.
Last night Ms Ponting, 28, a producer at the BBC World Service's Ukrainian service, was under armed police protection at a secret address.
Her husband, Gagic Ter-Ogrannsyan, was being told of the tragedy yesterday. He was convicted at the Old Bailey last year of murdering Ruslan Outsiev, the Chechen prime minister, and his brother, Nazebeck, in a London flat.
Last Thursday a local newspaper, the Woking News and Mail, revealed that Ms Ponting had issued a writ against Paul Condon, Commissioner of the Metropolitan Police, suing him for breach of copyright over a photograph of her in a bikini taken by her mother, Iris, that had been made available to the press at the end of her husband's trial.
Surrey police have been in touch with international law enforcement agencies via Scotland Yard. Last night, however, because so many questions remain unanswered about the killing, police had not relaxed their guard on the other homes in the area and had increased the number of patrols.
During the day a team of about 60 officers conducted house-to-house inquiries and searched wasteland in front of Mrs Reed's house.
Detective Superintendent John Stewardson, leading the murder hunt, said: 'It was an absolutely
callous assassination carried out in cold blood. She would have stood
no chance. It was very quick. It has all the hallmarks of a professional killing. It may well be a political
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