Harold Shipman is one of Britain's most notorious serial killers.
The former GP, who was well-liked and respected in his local community of Hyde, was found guilty of killing 15 patients and is suspected of murdering a total of 250.
BBC Two's new docuseries The Shipman Files: A Very British Crime Story, starting Monday 28th September at 9pm, delves into Shipman's crimes, examining why they went undetected for so long, and how the deadly doctor was eventually caught.
It transpires that Shipman made a series of chilling mistakes in the murder of his final victim, Kathleen Grundy, which lead to his arrest in 1998.
The murderous practitioner mainly preyed on the elderly, though it's thought his youngest victim could have been just four-years-old.
His tactic was to administer a lethal dose of poison to his victims, before doctoring their wills and walking away with their life savings.
In March 1998, three months before Shipman's final murder, Deborah Massey of Frank Massey and Sons funeral parlour and Brooke Surgery doctor Linda Reynolds both raised concerns about Shipman's patients with the coroner of South Manchester Distract.
Deborah was concerned by the suspiciously high mortality rate among Shipman's patients, while Linda was worried by how many cremation forms Shipman had countersigned.
However, the investigation that followed didn't find enough evidence to bring charges, which was subsequently closed.
Suspicions around Shipman remained, and were raised further by the strange circumstances surrounding by the death of his 81-year-old patient and final victim, Kathleen Grundy.
Shipman was the last person to see Kathleen before she was found dead in her home on 24th June 1998.
He recorded 'old age' as cause of death - but a series of glaring mistakes lead to the murderous doctor's undoing.
Kathleen Grundy, appeared to have cut her children out of her will and left £386,000 to Shipman.
The will read: "I give all my estate, money and house to my doctor. My family are not in need and I want to reward him for all the care he has given to me and the people of Hyde."
Kathleen's daughter, Angela Woodruff, a lawyer, realised that something was wrong and on the advice of her solicitor, Brian Burgess, went to the police.
An investigation was launched and Kathleen's body was exhumed.
When traces of heroin were found in Kathleen's system, Shipman tried to explain this with doctor's notes claiming his late patient was an addict - but on examining his computer, police found that these had in fact been added following the victim's death.
In addition, Shipman made two more mistakes. Kathleen's will had been forged on a Brother typewriter, which Shipman owned, and he also left a fingerprint on the will.
Shipman was arrested on 7th September 1998, bringing his 20-year reign of terror to an end.
He was found guilty of 15 counts of murder (though the suspected number of victims runs into the hundreds) and one charge of forgery on 31st January 2000, and received a life prison sentence.
On 13th January 2004, Shipman was found hanged in his cell at Wakefield Prison. The cause of death was deemed suicide.
The Shipman Files: A Very British Crime Story airs on BBC2 on Monday 28th September at 9pm.
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