Maimie Sinclair sat sobbing at the rear of the court as details of the little girl's death were read aloud. The seven-year-old had been sent to buy a bar of chocolate by the boy standing in the dock, the advocate-depute said.

When she returned, the teenage boy pinned her against the wall and "interfered" with her. She screamed for her daddy. The boy strangled her with a bicycle inner tube.

Maimie bowed her head. She could not bear to listen any longer. Her precious son, Angus, was a child killer.

It had begun.

Back in 1961, aged just 16, Angus Robertson Sinclair stood in the High Court in Edinburgh and admitted killing his seven-year-old neighbour, Catherine Reehill. Now 62, he has spent the past two weeks in the same court on trial for two of twentieth-century Scotland's most infamous murders.

Sinclair was cleared of those murders yesterday after the case against him collapsed. Nevertheless, he stands convicted of two killings, three rapes and numerous sexual assaults against young women. Police are not looking for anyone else in connection with the World's End killings and Sinclair is the chief suspect in four more murders. By his own admission, his assault victims may number in the hundreds.

Sinclair's record of sexual violence is unparalleled. Never in living memory has the country been menaced by such a dangerous sexual predator.

All but one of his crimes were carried out in the 14 years from 1968 to 1982, the period of his adult life when he was not behind bars. He has spent more than half his life in prison, and there can be little doubt that is where he will die.

However, Sinclair is not mad; that would make any attempt to understand him much easier. The disturbing truth is that his monstrous crimes were committed not by someone suffering from a sickness, but by a sane man.

Early years Angus Sinclair was born in the old maternity hospital at Rottenrow in Glasgow in 1945, a month after the war in Europe ended. He was the second son, the third child, of Angus and Maimie Sinclair.

Since the 1930s, the couple had lived in a tenement on St Peter's Street in St George's Cross, with their other son, John, and daughter, Connie. Angus snr was a journeyman joiner from Stirling; his wife the daughter of a coal miner from Salsburgh, a pit town near Shotts.

Post-war Glasgow was an overcrowded, blackened, smog-ridden city. The Sinclairs, like every family in their street, struggled to get by. In 1949, when Sinclair was four, his father was diagnosed with chronic lymphatic leukaemia. For the next two years, he watched his mother nurse his dying father.

Sinclair started school at Grove Street Primary, across the road from the family flat, in 1950. The smallest boy in his class, he was picked on from an early age. His father died in the Royal Infirmary a month before Sinclair entered P2.

Years later, after her son admitted killing Catherine Reehill, Maimie speculated that the death of his father may have damaged Sinclair mentally.

"Angus was so young at the time, but he missed his father terribly," she said.

"I keep wondering if that could have anything to do with what happened."

However, Sarah, Sinclair's estranged wife, has told The Herald that in all the time they were together, he never once mentioned his father. "I knew he had died when Angus was young, but he never spoke about his father," she said.

Those who remember him say he was an introvert, largely shunned by other children. Laurance Cumming lived in the flat next door and went to Grove Street school in 1953. "He was always a strange wee boy," he said.

Don Stuart also lived in St Peter's Street during the late 1940s. He emigrated to New Zealand and now lives in Auckland. He said: "Sinclair lived two or three closes down from me. He came from a very strange family. He was a wee smout. His sister Connie seemed okay and was a big girl, but he was very small."

Maimie, who stood by her son until she died in 1987, remembered a very different boy. After he admitted sexually assaulting and killing Catherine Reehill in 1961, she said: "The Angus I remember is not the boy who did this awful thing. The Angus I knew was a good son. He was a wonderful boy at home, but something happened to him. He seemed to change three years ago. I began to feel a bit frightened and worried about him."

The change was puberty, and with it came the onset of Sinclair's morbid obsession with sex and violence. Shortly before his 13th birthday, he started at St George's Road Secondary. His time there was deeply unhappy: boys bullied him and girls ignored him. He was a failure both socially and academically. One psychiatrist who examined him said he was "not a simpleton, but below average intelligence". As soon as he was legally allowed, he left school and got a job as a van boy. That was the summer of 1960, his last of innocence. Six months later, an eight-year-old girl was indecently assaulted nearby.

Peggy Reehill, 84, the aunt of the first girl killed by Sinclair, remembers: "He was caught interfering with wee lassies in Cowcaddens, people knew that about him at the time." Sinclair was arrested and charged with lewd and libidinous practices but, because he was only 15, he was placed on probation for three years. It was not enough to deter him.

First victim Saturday July 1, 1961, was a sweltering day. "Glasgow sizzles," said the front page of the Evening Times. The previous day, the Queen had been in the city, witnessing an old smoke-blackened tenement being demolished in the shadow of a new high-rise block.

On the Saturday, Maimie, Connie and John were all away from the flat. Sinclair was home alone when he saw Catherine Reehill skipping down the street. She, her six-year-old sister Margaret and brother Jim, five, were staying with their aunt while their parents, Patrick and Vera, were in London looking for jobs and a house. Patrick, a bricklayer from Hamilton, was planning a new life for his family.

Sinclair approached Catherine and gave her money to go to the shop around the corner. When she returned, he attacked her in the flat, then dumped her body in the close. She was found on the basement steps by two women on their way to the bingo. Within one minute, Sinclair appeared and volunteered to call an ambulance, telling the operator Catherine had fallen down the stairwell. There was blood on her nose and a large bruise on her forehead. She died in an ambulance on the way to the Sick Children's Hospital at Yorkhill.

A murder investigation was launched while the Metropolitan Police searched boarding houses in Fulham and Hammersmith for Catherine's parents. Sinclair had disappeared and this was noticed by the neighbours. Men took to the streets, looking for him. "If Catherine's uncles had got him that night they would have strung him up," said Peggy Reehill.

They did not, but the police did. He was arrested and charged the following day. On Monday morning, Sinclair, who had turned 16 just 24 days previously, appeared in the juvenile court in the old Partick Marine police station, as Catherine's parents arrived in Glasgow.

Maimie later claimed that he showed remorse while on remand. She said: "When I visited him in prison, he kept asking me, Why did I do it, mother? Why did I do it?' He said he was sorry for the heartache he had brought the little girl's parents, sorry for what he had done to me."

But the following month at the High Court in Edinburgh, when he pleaded guilty to the culpable homicide of Catherine, a psychiatrist said his conduct after the body was found was so normal that, in itself, it indicated a degree of abnormality. For this reason, coupled with his age, it was accepted that there was a degree of diminished responsibility. Sinclair was sentenced to just 10 years. He was out in less than seven.

Married man

While serving his sentence in Saughton prison in Edinburgh, Sinclair was given a trade and was granted day release during his last year inside. On his release, in 1968, he found work as a painter.

After his conviction, Maimie had said: "Now I will have to plan for Angus coming out and prepare a new life for him. He will change his name and we might emigrate." But he kept his name and the furthest he moved was back to Edinburgh. By 1970, he was working as a painter and decorator there. He spent two years living in a flat in Hill Place, off Nicolson Street - just one-third of a mile from the World's End pub.

Maimie and Connie, who remained devoted to Sinclair throughout his imprisonment, were thrilled when he met Sarah Hamilton, a student nurse originally from Townhead in Glasgow but living in nurses' accommodation at Edinburgh's Eastern General Hospital.

However, his older brother John, who is now in his seventies and living in the north of Scotland, had disowned him.

Sinclair, 25, and Sarah, 20, married in 1970 in the registrar's office in Leith. Connie and her husband acted as witnesses and both families were there, including Sarah's younger brother Gordon Hamilton, then aged 15.

After the wedding, the couple spent two weeks in Campbeltown on their honeymoon. Sarah, who remains married to Sinclair, was not told the real reason why John was absent. She now lives in a village in Dorset with her partner, but sees no need to get divorced. "It's just a bit of paper," she said of her marriage. "I don't have a bit of paper to say I'm divorced, and I don't have another bit of paper to say I'm remarried. I'm nothing."

Sarah remembers the day her husband told her he had killed Catherine Reehill. "That was well into our marriage," she said. "It floored me, big time. It was put across to me that he made a mistake and this young child died. That was a horror to me, but I was into my marriage by this time and I thought that I knew him. I looked at my brothers and other people in my life. They had all made mistakes; we all do when we're young."

She chose to believe Sinclair's version of events. "I put it down to him being a kid. I never looked at him as a child killer. I never looked at him suspiciously like he would ever do it again.

"In fact, if you walked into my house when he was living with me you would have said I was the volatile one. He wasn't violent, not at all."

Two years after they married, the couple had a son, Gary. By then, they were living with one of Sarah's brothers on Glasgow's Gallowgate. Sarah had become close to Maimie, who was overjoyed at the birth of Gary.

"I think she was happy he had settled down, he had a wife, he had a son, he worked hard," she said. "He was a hard worker. I worked hard as well, and eventually we had quite a nice lifestyle. We were making plans, as you do, to get ahead, but he had his own agenda."

Sinclair was having affairs - lots of them. When confronted by Sarah, he would always promise never to do it again. It was during this period, in the 1970s, that he bought an ice cream van to supplement his painting income and became interested in photography, even setting up his own darkroom. He also had a campervan which he took away on weekend fishing trips with brother-in-law Gordon Hamilton. At least, that is what he told Sarah.

The killing years On Saturday June 11, 1977, Frances Barker, 37, who worked for the City Bakeries, was dropped off outside her flat in Maryhill, Glasgow, by a taxi driver. Sixteen days later her body was found bound, gagged and half naked in a copse on a lovers' lane half a mile from the village of Glenboig, in Lanarkshire.

She was last seen outside 289 Maryhill Road. At the time, Sinclair was living with his mother at number 375 on the same street.

Eight weeks later, on the night of Friday August 5, 1977, Anna Kenny left the Hurdy Gurdy pub in Glasgow's Townhead and was never seen alive again. She and a friend Wilma Sutherland had been at the bar, on Lister Street, where they met two young men.

Lister Street is just a short walk from Stirling Road in Glasgow, where Sarah's family lived. Her brother, Gordon, was born in the Stirling Road flat and had left home only three years previously, when he was 19.

At closing time, Anna, 20, left the pub with one of the men, who offered to walk her to George Square, from where she could get a bus. She never returned home. Police traced the man she was with, who told them she had left him to find a cab and that after she had turned a corner out of sight, he heard a car brake and assumed she had either hailed a taxi or been spotted by someone she knew.

Her remains were found by two shepherds, 21 months later. All that was left was her skeleton and some material, which later proved to be the shirt she was wearing at the time of her disappearance.

It had been bound around her neck and ankles. The discovery was made in two feet of soil in Skipness, a village on the Kintyre peninsula on the road to Campbeltown, where Sinclair spent his honeymoon.

Two months later, on Friday October 1, Hilda McAuley, a divorced 36-year-old mother of two young children, was seen leaving the Plaza Ballroom at Eglinton Toll in Glasgow.

The next day, bramble pickers found her half-naked, badly battered body lying in long grass opposite the entrance to the West Ferry caravan site, 16 miles away in Langbank, Renfrewshire. The area was known locally as lovers' lane.

Her clothing was scattered among the bushes and police discovered that her coat, shoes and handbag were missing. Stealing items of clothing and other possessions was Sinclair's signature.

A fortnight after Hilda McAuley's murder, two young friends in Edinburgh met up for a Saturday drink after work in a pub where the High Street runs into the Canongate: the World's End.

It was a popular pub and that Saturday, like every weekend, it was standing room only, with 200 people packed into the small bar. It was a time when a drink cost less than £1, last orders were before 11pm, and Baccara's Yes Sir, I Can Boogie was at number one in the charts.

Christine Eadie and Helen Scott, both just 17, were on a girls' night out with two more friends. They turned down an invitation to a party from the other girls and remained in the pub until it closed.

On the street outside, they encountered two men, who persuaded the girls to go to a party with them. They were never seen alive again, their half-naked bodies turning up six miles apart in East Lothian, on a beach and in a field. Clothes from both Helen and Christine were missing, as were their handbags.

Seven weeks later, Agnes Cooney, a 23-year-old children's nurse, spent the afternoon of Friday December 2, 1977, flat-hunting with fellow nurse Gina Barclay. They then went to the Clada Social Club on Westmoreland Street on the south side of Glasgow.

Agnes had a few drinks and, just after midnight, said she was going home. Her body was found the following Sunday, 20 yards away from Snipe Road near Caldercruix, Lanarkshire, by a farmer. She had been stabbed 26 times.

Within two weeks, police publicly linked her murder with Hilda McAuley's. Both had their hands tied behind their backs and both vanished as they left places of entertainment to find a taxi.

At the time, Sinclair was splitting his time between his mother's flat in Maryhill and a flat at 30 Daisy Street, in Govanhill. Hilda McAuley and Agnes Cooney were last seen near the Daisy Street flat: Agnes Cooney 350 yards away, and Hilda McAuley within three-quarters of a mile.

Sinclair has not been charged with these murders, but his estranged wife, Sarah, has been taken to the places where the women were last seen and the bodies found. "This will go on for years," she said. "It won't be the end, the police have told me. The case against him will never close until they have put him with those girls in Glasgow. They know he did it. He did it, I'm convinced. I've been to the sites, I've been everywhere with the police. They are all places where he could have been."

In November 1978, Mary Gallacher, 17 and just 4ft 11in tall, was murdered. Her body was found at the foot of a 20ft wall near a footpath crossing waste ground between Flemington Street and Edgefauld Road in Springburn, Glasgow.

She left home in Endrick Street at 6.45pm one Sunday night to meet two friends and was cutting across the path to get to Avonspark Street and the home of one of them. She never made it. Sinclair held a knife to her back, made her take off her clothes, strangled her with the leg of her trousers, raped her and slit her throat three times. Once again, her handbag was missing. Sinclair would not be caught for another 23 years.

Sexual predator Sinclair was known to the police during the 1970s, as a thief, housebreaker and violent mugger. On one occasion he mugged a woman after smashing her in the face with a claw hammer; on another he cleaved a man with a hatchet. He did not give the people he mugged an opportunity to hand over their money, simply attacking them without warning and emptying their bags and pockets.

Sinclair had stopped paying tax and National Insurance by 1974, yet was buying new cars and had money to spend. In 1979 he was convicted of possessing a handgun and was sent to jail for six months. Sarah left him briefly, but the couple got back together when he was released. They moved in with Maimie, by now 74 and not in good health, and Heather Rees, Connie's daughter, in a semi-detached house on Wyndford Drive in Maryhill.

In 1980, after he was released from prison for the firearms offence, Sinclair and Sarah put down £3000 as a deposit on a Barratt home in a new estate in South Nitshill in Glasgow, for which they paid £27,250. But, during this period, police began to see a pattern linking a series of rapes and sex attacks on young girls across Glasgow.

One day in June 1982, a young girl was lured into a close in Govanhill, but escaped screaming when she realised she was going to be attacked. Later that same day, a seven-year-old girl in her swimsuit was sexually assaulted in a close in Partick.

In the same month, a girl of six was raped in the Woodlands area of the city. She vividly remembered that the man's shoes were splattered with green paint. Another young girl remembered the man who attacked her as smelling of turpentine. Sinclair was identified by one of the young girls from a photograph shown to her by police.

Sarah remembers the day when the police arrived on the doorstep of their home on Craigflower Road. Sinclair was charged with three rapes and nine sexual assaults. His victims were all girls aged between six and 14.

His own son, Gary, was just 10 at the time.

Sarah said: "When he abused all of those children, he initially denied it to the police. I went to see him and I told him, You are going to admit what you've done. You're not going to drag us through a court case'. Well, he did admit to them."

He told Sarah he had lost count of the number of girls he had attacked, and he had been doing it for years. Asked by detectives how many there were, he said: "I have done so many I can't remember all I have done. I honestly can't.

"It might be 50, it might be 500. If you can find out where and when, I'll tell you whether I did them or not."

Life sentences for rape are rare in Scotland. However, Lord Cameron was certain that he could pass no other sentence. "The penalty for rape is entirely discretionary and without limit," he told Sinclair. "I have considered very carefully whether a limit should be placed on the extent of the penalty, and I have decided there is only one limit - namely your life."

Disowned Sinclair has never left prison since, except for court appearances. He has spent 32 of his 62 years incarcerated. Following the conviction in 1982, his mother, sister and niece, Heather, again stood by him, faithfully making the long journeys to Peterhead.

However, after advances in DNA technology he was charged with, and convicted of, Mary Gallacher's murder. He was identified when a sample of hair taken from the original post-mortem examination was tested. Neither Connie, now widowed and living in Erskine, nor Heather, still living in the house in Maryhill, have visited him since.

Maimie Sinclair never accepted the truth about her son. She died of a heart attack in 1987 aged 81. She had a long life and a quiet death in her own home. The same cannot be said of Sinclair's victims.