But she was being watched. As she walked across the bridge on the outskirts of Coldstream, Robert Black, a convicted sex offender with a lifelong history of paedophile perversion, moved in. He heaved her into the back of a Ford Transit van and inside, hidden from view by curtains, subjected her to a violent sexual attack. He then killed her.
When her body was found in a copse 15 days later, 264 miles away near a lay-by on the A518 at Locksley in Staffordshire, it was too decomposed for the cause of death to be established.
Nearly a year later, in July 1983, Black struck again. His victim was Caroline Hogg, 5, whom he abducted near her home in Portobello, Edinburgh. Twelve days later, her naked body was discovered 308 miles away in a ditch at a lay-by off the A444 near Twycross, Leicestershire.
The two murders, clearly linked, prompted a huge but fruitless police inquiry involving six forces in England and Scotland. Much time was spent searching for a red Triumph car, seen south of Coldstream when Susan Maxwell disappeared and again near to where her body was found.
The investigation had ground to a halt by the time Black struck again. On 26 March 1986, he snatched Sarah Harper, 10, who was on brief shopping round near to her home in Morley, near Leeds. After raping and beating her, Black dumped her, alive but probably unconscious, into the river Trent more than 80 miles away, where she was left swirling around a weir. Her body was found on 19 April.
There were obvious connections with the Maxwell- Hogg inquiries and all three girls had been stripped of their white socks and shoes, possibly as trophies. The largest serial child-killing inquiry in Britain was under way.
The investigation would span eight years, with 60,000 statements being taken and 185,000 people questioned. Thirty-eight police officers and 24 typists worked on 50 computer terminals linked to the Home Office Large Major Enquiry System (Holmes).
The FBI was called in to help build a psychological profile of the killer and one witness agreed to be hypnotised in an effort to identify important details.
Despite these efforts, however, the inquiry was dogged by missed chances.
Black's Ford Transit was never traced despite later confirmation that he had been in Coldstream when Susan Maxwell went missing, in Morley outside Sarah Harper's home, in Nottinghamshire where Sarah's body was found, and in Radford, Nottingham, where he attacked a girl.
Although the police were correct in believing a lorry driver - or someone with a reason to travel long distances - would turn out to be the killer, they appear not to have conducted sufficient checks. Had they drawn a limited 'circle' around each site and checked on drivers who were delivering or calling near by, they would have discovered that Black, a convicted sex offender, was always there - in his company's Transit van.
Police said later that it was an 'impractical task' to try to trace the Transit, one of 690,000 in the country. However, a check with companies close to two of the abduction sites would have produced the identity of Black as a regular delivery driver using a white Transit van.
When Teresa Thornhill was attacked in Radford, Nottinghamshire, in April 1988, Black was delivering to a firm 475 yards away and his van was filmed - but not identified - on a bank security camera. Details of this attack were not passed on to the police inquiry.
Black, despite his convictions in Scotland, was not in the police list of suspects with records for child sex offences because it was decided not to include minor crimes - which would have involved an additional 33,000 names.
At that time the police also had a highly likely suspect whom they referred to as Mr X and they prepared a 118- page criminal investigation report on him before dismissing him.
Like most serial killers, Black was eventually caught because he carried on offending, rather than as a result of diligent police work.
In July 1990, a six-year-old girl was on her way home when Black pulled up alongside her and dragged her inside his van. A neighbour who saw the incident and took the van's number, alerted the girl's family and the police.
In the van, Black taped the girl's mouth, placed a hood over her head, tied her hands and feet and forced her into a sleeping bag. He tied the neck of the bag tight - as had been done in the other three cases - then forced it behind his driving seat. He also indecently assaulted her.
Lothian and Borders police blocked all roads in and out of the force area. The van was spotted by the girl's father; when police stopped the vehicle he rescued the child who had only minutes to live.
By a stroke of luck, petrol receipt records for Black's company had not been destroyed and police were able to log precisely where Black bought petrol.
The police were also able to check Black's company food bills, cash-machine withdrawals and credit card records. The checks led directly to his conviction. There was practically no hard evidence against him, no forensic evidence and no confession.Reuse content