Donald Neilson, who died on Sunday, was an ex-soldier who planned his murders like military operations.
He became a career burglar and then killer using covert skills and survival tactics learned during jungle fighting for the British Army.
The calculating criminal, one of a small group ordered to live out their days behind bars, was known as the Black Panther because of the black hood he wore and speedy movements recalled by victims of his attacks.
His lucrative crime spree - which included the murder of a Black Country sub-postmaster and culminated in the kidnapping and killing of teenage Shropshire heiress Lesley Whittle in 1975 - was thought to have been fed by his repeated failure to hold down work to support his family.
But his appetite for violence and guns stemmed back to his teens in the 1950s.
Neilson, whose mother died when he was 11, enjoyed "anything where he could show his physical prowess", Jerry Corfield, a boyhood schoolfriend, told reporters in 1976.
Neilson, born in August 1936, was said to have relished life during National Service in Kenya, Aden and Cyprus.
But his wife Irene persuaded him to leave the services and settle down in Bradford ahead of the birth of daughter Kathryn. In 1960, he changed his name by deed poll to Neilson from Nappey.
His life of crime began after a string of failed business ventures. He struggled to earn a living as a carpenter before his taxi and security guard firms both flopped.
By the mid to late 1960s he was carrying out hundreds of burglaries to supplement his income.
Lucrative rewards continued to elude him, however, so he turned to armed robberies at sub-post offices.
His first-known gun attack took place in February 1972 when he broke into a sub-post office in Heywood, Lancashire. But postmaster Leslie Richardson survived gunshot wounds after confronting hooded Neilson.
Two years later the killings began when he broke into a sub-post office in Harrogate and shot dead Donald Skepper.
He then claimed another life, that of Derek Astin, in almost identical circumstances in Higher Baxenden, near Accrington, before adding a third by shooting Sidney Grayland, 55, at his sub-post office in Oldbury, in the West Midlands.
Police carried out thousands of interviews in the search for "The Black Panther".
But national interest would be intensified when he kidnapped Lesley to earn a ransom fee.
Having read an article in the Daily Express about £82,500 she inherited when her father George, who ran a coach company, died, Neilson broke into her home in Highley, Shropshire, and quietly abducted her from her bedroom.
Her naked body was found days later after she plunged into a deep drainage shaft beneath Bathpool Park, near Kidsgrove, in Staffordshire.
Neilson remained on the run for another nine months before officers spotted him acting suspiciously near a sub-post office in Mansfield, Nottinghamshire.
As Pc Stuart McKenzie challenged him, Neilson pulled out a double-barrelled shotgun, forcing the officer and his colleague, Pc Tony White, to drive off at gunpoint.
But the officers, joined by passer-by Roy Morris, eventually overpowered him in a violent struggle. He appeared battered and bruised in police mugshots.
After his capture, a cache of guns, ammunition and even a model of a black panther were found at his Yorkshire home.
Neilson then confessed his crimes and said that he had accidentally knocked Lesley off the ledge of the drainage shaft.
He was given four life sentences in July 1976 and told by a High Court judge in 2008 that he would never be freed from jail.
Neilson's health had been deteriorating for some time - in 2008 it was reported he was suffering motor neurone disease.
He died on Sunday after being taken from Norwich Prison to hospital with breathing difficulties, prison sources said.