He has been, for half a century, “the most hated man in Britain”, the walking embodiment of evil, an unrepentant Antichrist and exhibit No 1 in the argument for bringing back the death penalty. Now he has departed in a final irony: the man whom many would have cheerfully killed with their bare hands was denied for years by medical science and the laws of the land his desire to end his own life.

Ian Brady was the main protagonist in the Moors murders, a title that now has the echo of an old horror film rather than the grim reality of the killing of five children – Pauline Reade, John Kilbride, Keith Bennett, Lesley Ann Downey and Edward Evans. Along with his accomplice, Myra Hindley, who died in prison in 2002, Brady represented the darkest side of the national psyche: unredeemed and unredeemable. But why has he cast such a baleful shadow for so long when other child killers, sexual torturers and savage pyschopaths have been able to slide off into the relative obscurity of psychiatric wings and solitary confinement? Why was it that Brady was able to embody for so many the almost biblical notion of evil?

“It’s much easier to think that Ian Brady was evil, because he is then not someone like ‘us’,” says Coline Covington, the forensic psychologist and author of Everyday Evils, a Psychoanalytic View of Evil and Morality. “What’s difficult is to identify with him in any way – [to recognise] that we may all at least have fantasies of torturing and killing, although most of us don’t act on them. We project whatever is evil and sadistic on to the criminal so that we can remain unsullied and pure.”

Police searching on Saddleworth Moor in October 1965. Photograph: PA

Although it was Brady who initiated and carried out the murders, in many ways it was Hindley who was regarded as even more reprehensible, a role she herself both recognised and rejected. In December 1995, after she had been described as a psychopath in an article in the Guardian, she wrote a long essay to the paper in which she herself even appeared to take a greater share of the blame.

“I was corrupt, I was wicked and evil,” she wrote, “without me those crimes could probably not have been committed. It was I who was instrumental in procuring the children, children who would more readily accompany strangers if they were a woman and a man than they would a man on their own … I take full responsibility for the part I played in the offences, and will not attempt to justify the unjustifiable.”

Hindley’s gender almost certainly meant that she was the more reviled – her crimes being “unwomanly” – and she clearly resented being cast in a role that Brady himself seemed almost to relish: “In spite of hundreds of other females in the system who have been convicted of quite horrendous crimes, the tabloids have turned me into an industry, selecting me as the public icon/evil monster, Medusa-like image which holds the projected hatred, fear and fury of the nation’s psyche,” she wrote. She claimed that she satisfied the desire for there to be a “national scapegoat”.

And, in a way, she and Brady together fulfilled for the British public the role the paedophile or sex offender fulfils for other prisoners in jail – someone they could hate and despise without restraint: “At least, whatever we did, we’re not as evil and horrible as that.”

In the US, Charles Manson has filled the same role for Americans since he and his band of followers carried out their murders in California in the 1960s. Like Brady, Manson outraged people not just for his crimes, but for his chilling arrogance and the very detached way he perceived himself and presented himself to the public, with a swastika on his forehead and his contempt for society. Manson liked to tell reporters that he would never be let out of prison because Americans were frightened that he would “break their toys”. Brady appeared to enjoy having the same national aura, rejecting medical diagnosis of his psychopathy and dismissing the doctors who treated him as “irrelevant worms”.

Myra Hindley on the moors in a photograph taken by Brady. Photograph: HO/AFP/Getty Images

Britain has a fascination with murder and murderers, not least because there are remarkably few of them per head of population, and most are mundane and swiftly solved. Judith Flanders in her study of the phenomenon, The Invention of Murder, attributes that national interest as “like hearing the blustery rain on the window pane when sitting indoors”. It would be impossible to imagine a week of British television without a fictional or factual exploration of murder. Serial killers? Sexual predators? We lap them up, the grimmer and more sadistic the better. So when we have a real-life ogre, apparently repulsive in every way, to focus on, so much the better. Every year seems to bring us a new book about Jack the Ripper, a killer whose murders were so grotesque that they were described in the press at the time as “too horrible to describe or even hint at”. No wonder the sales of newspapers covering such gruesome crimes shot up.

The other factor that kept Brady alive in the public imagination was that he so narrowly escaped the noose. MPs voted by 355 to 170 to bring an end to capital punishment in 1964, with the act becoming law in 1965, the year before Brady and Hindley went to trial. The debate about whether or not the death penalty should be brought back continues to this day, although most governments would be wary of offering a referendum – the “will of the people” – on the subject. Before Brady, perpetrators of unspeakable crimes were, if caught, almost all executed. Hence the likes of Neville Heath, who butchered young women and was hanged in 1946, and John Haigh, the “vampire killer” who dissolved his victims’ bodies in an acid bath and was executed in 1949, were dispatched long before their presence on Earth could be regarded as an offence to the relatives of their victims. Peter Manuel, “the Beast of Birkenshaw”, who murdered at least seven people in Scotland, was hanged in Barlinnie in 1958. Brady’s mother, Peggy Brady, who had to give her son up for adoption as a child, may have told the Daily Mirror in 2000 that “he has learned his lesson but he is being kept inside because his name is so famous, like Jack the Ripper or Dr Crippen” – but the former was never identified and the latter was hanged.

Any debate over capital punishment since its abolition has almost inevitably involved mention of Brady and Hindley but, in fact, a survey carried out in March 2015 indicated that support for the death penalty in Britain had finally dropped below 50%. According to the annual NatCen British Social Attitudes Report, 48% were in favour, the lowest figure since the survey began in 1983, when about 75% of people supported hanging for murder.

Brady had wanted to die for many years and, given that prisoners now take their own lives so regularly – 119 in the last year alone, a rate of around one every three days – you wonder why he was never quite able to manage it. This also raises the issue of whether he enjoyed playing with the media version of himself. He was certainly more than conscious of his image and how he was portrayed in the press. When the late Jimmy Nicholson, the crime reporter known as “the Prince of Darkness”, wrote a disparaging piece about him not long after his conviction, Brady duly complained to the Press Council and then sent Nicholson a “wish you were here” card from Parkhurst prison. In 2012, it was reported by the Daily Mirror that Brady had boasted to a lawyer representing the family of one of his victims that he was regarded as more important than Peter Sutcliffe, the Yorkshire Ripper: “He’s had 34 mentions in the press this year,” he told the lawyer. “I’ve had 144. Why do you think I’m still top of the ratings after 40 years?”

So who now fills the gulf of revulsion left by Brady? Considering her much longer history of violence against defenceless young women, Rosemary West has escaped much of the opprobrium attached to Brady and Hindley; and her husband, Fred, accomplished Brady’s wish of suicide before he even stood trial. Sutcliffe is ill and has been moved from Broadmoor to prison. Serial killer Levi Bellfield has already been attacked in prison and may be a candidate for Brady’s mantle. Murder trials are no longer reported in such great detail as they were in the 1960s, so the names of killers slip in and out of the national consciousness in a way that did not happen in the past. But we will never have heard the last of Brady and Hindley.