The middle one of three children, Freddy was his mother's favourite. A mediocre student, with some athletic prowess, he found it difficult to make friends. This was not helped by his over-protective mother, Vera, who vetted his acquaintances and organised his personal life.

He worshipped her and was devastated when she was struck down with lung cancer. Every day he would come home from school, make her a cup of tea and chat to her as she lay in bed wracked with pain.

The young Freddy no doubt marvelled at the morphine which gave his mother such instant relief from her agony when it was injected by the family GP. Perhaps, at this most impressionable of ages, Freddy decided he would like to be the angel of mercy dispensing this magic medicine to people in need.

His mother died in June 1963, when Freddy was 17.

Two years later he was admitted to Leeds University medical school. He struggled with academic life but eventually ground out a degree and got his first job as a hospital intern. Shipman settled down with his new wife, Primrose, who was three years his junior and a "homely" type.

She was five months pregnant when they married but it was not a shotgun wedding and there was no doubting their deep and mutual affection. In 1974 Shipman took up his first GP's position in the small Yorkshire town of Todmorden. He fitted in well with the residents, but did not suffer fools gladly and would often give his staff a tongue-lashing if they made mistakes.

At home Primrose was raising a growing family and everything seemed set fair for a prosperous life for the Shipmans.

Then, in 1975, disaster struck.

The first signs

A suspicious receptionist, Marjorie Walker, noticed some odd entries in the controlled narcotics ledger of a local pharmacist. Large quantities of pethidine, a morphine-like painkiller used in childbirth, had been ordered by young Dr Shipman.

The practice's senior GP, Dr John Dacre, investigated and found many of the patients Shipman was supposedly ordering on behalf of had never been prescribed or had any need for pethidine. At the same time staff noticed Shipman, then aged 29, was suffering blackouts which, he claimed, were due to epilepsy.

Dr Dacre confronted Shipman, who confessed he had been injecting the pethidine into his own veins. He begged for a second chance, but then stormed out and threatened to resign. But he did not quit and was eventually forced out and ended up in a drug rehabilitation centre.

Shipman was fined £600 for forgery and prescription fraud but, crucially, was allowed to continue practising as a GP. When his later crimes were uncovered new questions were asked about his time at Todmorden. There are some who believe Shipman's confession to drug-taking was actually a ruse to cover up the beginnings of his murderous career.

In 1977 Shipman, apparently cured of his addiction to pethidine, was offered a job at the Donneybrook Medical Centre in Hyde, a nondescript suburb of Manchester. He was perfectly upfront with his new colleagues, to whom he said: "All I can ask you to do is to trust me on that issue and to watch me." Soon he had earned the trust and respect of his colleagues and his new patients. He was hard-working, conscientious and had a warm bedside manner. Shipman's problems appeared to be behind him and his previous convictions were soon forgotten.

Over the next 20 years Harold Shipman killed with impunity.

236 murders

The Department of Health's best estimate is that he killed 236 patients between 1974 and 1998. It seems remarkable that one GP could have so many more patients dying than his colleagues without anyone noticing.

Over the years doctors, funeral directors and pharmacists had made mental notes about Shipman and some had even mentioned it out loud. One, undertaker Alan Massey, even confronted Shipman head-on but the good doctor's response was so calm and reassuring that Mr Massey dropped the matter.

Shipman might have carried on killing for years if it had not been for Angela Woodruff.

When her mother died at the age of 81 she could have been forgiven for accepting it as sad but inevitable. But Mrs Grundy, a former Mayor of Hyde, was energetic and healthy and her death on 24 June 1998 was totally out of the blue. She was found on the sofa at home by friends at an Age Concern club, who called on her when she failed to turn up.

The last person to see her alive was Dr Harold Shipman, who had purportedly gone to her home to take routine blood samples.

Shipman told Mrs Woodruff there was no need for a post mortem because he had seen her shortly before she died. Mrs Woodruff, distraught, accepted his words and her mother was laid to rest in the town's cemetery.

But Shipman had made a massive mistake.

The mistake

He had forged Mrs Grundy's signature on a new will, which left £386,000 to none other than Dr Harold Shipman. Mrs Woodruff, a solicitor herself, was puzzled. Her mother had made a will in 1986, which was lodged at her own law firm. She naturally became extremely suspicious when it emerged that a new will had been made without her knowledge. It was inconceivable that her mother would not have left her a penny.

She was forced to conclude that Shipman had murdered her mother for profit and she immediately went to the police with her suspicions. Detective Superintendent Bernard Postles was the man assigned the job of investigating Dr Shipman. It was a delicate task, as he was a respected member of the community. But Det Supt Postles said he was convinced Mrs Woodruff was right when she showed him the new will.

He recalls: "As soon as we looked at those documents, and the quality of them, the typing that was on them, the phraseology, it was apparent to us that they had been put together by someone other than Kathleen Grundy."

Det Supt Postles, whose team was receiving more and more information about Shipman and his callous behaviour towards patients, obtained an order to exhume the body of Mrs Grundy, so it could be forensically examined. The exhumation, carried out in the dead of night, alerted the national media to events unfolding in Hyde and journalists began to descend on the town.

Det Supt Postles investigated Shipman, who was contemptuous of the investigation into him and denied any wrongdoing. But his story was unravelling. Police discovered he possessed an old Brother typewriter which matched the type used on the counterfeit will.

Desperation

Knowing he was in a tight spot, Shipman came up with a preposterous story about how he had lent the typewriter to Mrs Grundy. As news of the investigation into Dr Shipman leaked out, various undertakers and other doctors came forwards with their suspicions about his high death rate.

Police went through his book of death certificates with a fine toothcomb and made a list of 15 deaths which they decided should be investigated as a priority. Of the victims on this list, nine had been buried and six cremated. More exhumations were ordered and police also learned that Dr Shipman had often encouraged the relatives of his victims towards cremation.

The police enquiry would also reveal Shipman's modus operandi.

He would often kill his victims - most of whom were elderly - with an injection of morphine and then return to his office to falsify their medical records on his computer to exaggerate their poor health. In the case of Mrs Grundy, he had backdated several entries to suggest she had become addicted to morphine. Again Shipman was undone by his arrogance and ignorance.

He was unaware that an expert, Detective Sergeant John Ashley, would be able to examine his computer hard drive and find out exactly when he made an entry in his patients' records.

This would provide damning evidence to the jury.

On trial for murder

The trial began in October 1999 at Preston Crown Court, about 50 miles north of Hyde. Shipman's barrister, Nicola Davies, initially attempted to have the trial halted because of "inaccurate and misleading" coverage in the press.

She failed.

Ms Davies then sought to have the case of Mrs Grundy severed from the other murders because it, alone, had an obvious motive.

She failed.

She then sought to persuade the judge to exclude from the jury evidence that Shipman had stockpiled morphine, often by prescribing in the name of patients who were already dead.

Again she failed.

Prosecutor Richard Henriques QC, who had represented the Crown in the same court six years before in the trial of the two boys who killed Liverpool toddler James Bulger, began his opening address to the jury by ruling out euthanasia. None of the 15 victims had a terminal illness and he did not want the jurors to get it into their heads that Shipman may have been motivated by mercy.

But he was aware that the jury would need some idea as to motive. Mr Henriques explained as best he could: "He was exercising the ultimate power of controlling life and death, and repeating the act so often he must have found the drama of taking life to his taste."

Mrs Woodruff then took the stand and spoke of her mother as a picture of health: "We would walk five miles and come in and she would say 'Where's the ironing?' We used to joke she was fitter than we were." Ms Davies' cross examination focused on Mrs Woodruff's wealth - her husband had inherited £1m - but did nothing to undermine her testimony. Pathologist Dr John Rutherford then led the jury through the evidence obtained from the post mortems on the nine exhumed victims. He pointed out they had not died from old age or natural causes. Dr Rutherford was adamant as to the cause of death in each case - morphine toxicity.

A handwriting expert was up next and he stated unequivocally that the signatures on the will were "crude forgeries". Det Sgt Ashley then testified about the tell-tale clues on Shipman's computer hard drive. The next witness, district nurse Marion Gilchrist, wept as she recounted how Shipman had confided in her as Mrs Grundy was exhumed: "The only thing I did wrong was not have her cremated. If I had her cremated I wouldn't be having all this trouble."

Witness after witness, many of them victim's relatives and friends, painted a picture of a callous and deceitful man who was a compulsive liar. When it was the defence's turn they sought to portray Shipman as a kind and caring family doctor and a true professional. She pointed out he was happily married with four children. Ms Davies attempted to undermine the forensic evidence but it was an impossible task to make any inroads into the mountain of proof.

On the afternoon of 31 January 2000 the jury returned with a unanimous verdict. Shipman was found guilty on all 15 counts of murder and also of a forgery charge. Sentencing him, Mr Justice Forbes said: "You murdered each and every one of your victims by a calculated and cold-blooded perversion of your medical skills, for your own evil and wicked purposes.

"You took advantage of and grossly abused their trust. You were, after all, each victim's doctor. I have little doubt that each of your victims smiled and thanked you as she submitted to your deadly ministrations."

The judge handed out 15 life sentences and told Shipman he would be recommending to the home secretary that he never be released. With the trial over work began on estimating Shipman's true death toll.

The Public Inquiry

Professor Richard Baker, of Leicester University, who carried out a clinical audit for the Department of Health, concluded Shipman had been responsible for the death of at least 236 patients. Most of these were elderly women who died in their homes. In 2002 a public inquiry chaired by Dame Janet Smith opened in Manchester.

It was given the task of looking at what went wrong in the Shipman case and was asked to come up with recommendations about changes that need to be made. Dame Janet, speaking in January 2003 during a break in the inquiry, said there was a need for changes in the way deaths were scrutinised. She said the system was "inadequate and must be changed to meet the needs of society in the 21st century".

At that time coroners did not have to be involved and post mortems were not required, if the deceased had recently seen a doctor or been in hospital. If the body was to be cremated a second doctor had to sign a form. But Dr Norman Beenstock, a former GP in Hyde who countersigned 18 cremation forms for Shipman, said doctors rarely asked questions of each other and often had blind faith in their peers.

He said: "I was reliant on what Dr Shipman told me and I would have trusted a fellow GP to have been honest and open with me."

The Shipman Inquiry criticised the police's handling of the case. In their initial police inquirys two officers "found no cause for concern" and ended their investigations after three weeks. Dame Janet called for "radical reform" of the way coroners work in England and Wales.

The General Medical Council has already moved to introduce reforms regulating doctor performance, which it says will prevent a similar case.

On Tuesday the 13th of January 2004 Shipman died after being found hanging in his cell in Wakefield prison.

This profile of Harold Shipman was written by BBC News Online's Chris Summers.