What is clear is that he had a disturbed, loveless upbringing, seemed unable to make proper friends and appeared unattractive to those who knew him. At work he was 'Smelly Bob'; at home, he kept a vast library of paedophile material.
Although willing to acknowledge this perversion and to admit the abduction of a young girl in 1990 - when he was caught in the act - Black has never divulged any details of the murders for which he was found guilty yesterday, despite hours of intensive police questioning.
Black was born in Falkirk Royal Infirmary in April 1947, the illegitimate child of a Grangemouth woman. After being abandoned, he was placed with foster parents and grew up in the small Highlands town of Kinlochleven. Frances Daley, who works in the local baker's shop, was in the same class: 'He was always a tough wee boy and I did get the impression that because he had been given a hard time in his early life he had decided he had to stand up for himself because no one else would.' Sandy Whillans, the former village policeman, remembers that Black always needed to be 'kept in line'.
His foster mother died when he was 13 and Black went to a hostel for the homeless in Musselburgh, near Edinburgh, where he is said to have been sexually abused. He was neglected, had virtually no friends and often inspired intense dislike.
Although there had been earlier suggestions of his unhealthy interest in young girls, it was not until he was 16 that Black was charged with 'lewd and libidinous practices' with a young girl; he was admonished by Greenock Sheriff Court. Four years later, at Oban Sheriff Court, he admitted three indecency charges and spent two years in borstal.
After school, he had worked as a swimming pool attendant; police now feel he might well have been using his work to spy on girls.
When he was 21, Black moved to London and for 19 years lodged in Stamford Hill with Edward and Kathy Rayson, and their seven children. When police searched his room they found a vast collection of pornographic films, three video recorders, magazines and a publication known as Unsolved, dealing with unsolved murder cases, including child killings.
One of the Rayson's sons, Raymond, once discovered a suitcase full of pornographic magazines and photographs of young children and small swimming costumes in Black's room. Despite this, neither he nor his parents suspected Black of being a child killer and regarded him as the 'perfect tenant'. Only once in 19 years did he take a girlfriend to the house.
Some of Black's workmates at PDS (Poster Delivery Services) were suspicious of him. One of them once thought his daughter was being abused by Black.
Another man who worked with Black was so troubled he quizzed him about his movements after the Susan Maxwell disappearance. Black lied and his workmate did not pass on his concerns.Reuse content