Police officers spotted a red Vauxhall Cavalier just outside Barnesbury Farm, an estate of about 600 red-brick houses, many of which have been bought from the local authority.
It was followed around the estate and the two policemen were just about to stop it and question the driver when he stopped and leapt out, leaving the lights on and the engine running as he escaped across waste ground towards Woking Football Club's ground.
An examination of the car later revealed a pistol, on which police are still carrying out tests, and a map bearing a number of pencil lines which appeared to suggest a number of addresses in the area.
From the scant information available, the police identified at least five households in the area, including Karen Reed's home, which could have been vulnerable because of their occupants' past, their associates or their jobs.
All the homes were fitted with 'state of the art' alarm systems with panic buttons which allowed them to call police for help at any time and armed officers were also detailed to patrol the small area around the clock. But on Saturday evening the gunman struck.
Mrs Reed, a geophysicist, who worked a few miles away in Addlestone, Surrey, answered her front door shortly before 9pm just as it was getting dark.
As she opened the door of the double-fronted corner house, the man fired four or five bullets into her.
Jerry Buckley, 38, was outside his house a few doors away polishing his car with his son Nathan, eight, when the shots rang out in the quiet road.
His mother-in-law Margaret Fuller, 62, who was in the house watching television at the time, said: 'They said it was just bang, bang, bang . . . There were four or five shots and screaming. Another woman who was in the house closed the door and the man ran off.
'Jerry just grabbed Nathan, who was crying, to shield him from what had happened. He came banging on the door to be let in.' She said that for quite a few minutes after the shooting, the house, which is always well lit at the front, remained quiet before the woman inside finally opened up with the arrival of an ambulance and shortly afterwards some police. But Mrs Reed was pronounced dead at the scene.
Detective Superintendent John Stewardson, leading the murder hunt, said that none of the sophisticated alarm equipment had been activated, but since the woman who was behind the victim at the time of the attack was a visitor that was not surprising, as she may not have known of its existence.
The murder victim was said to lead a quiet life at her renovated home. Her neighbours had never met her although she had lived there for some time.
On Saturday night, Miss Ponting, a BBC radio producer for six years, was at Bush House in London where she was due to have been until 10am yesterday morning.
Not long after her shift had begun she was called away urgently leaving colleagues mystified, only later discovering to their horror that her older sister had been the victim of what was probably a professional hit man as she spent a quiet Saturday evening in her home.