Dennis Nilsen – who was born in Fraserburgh and in 1983 was convicted of six murders and two attempted murders and is believed to have killed at least 15 men and boys – defies categorisation. He abhorred cruelty to animals, yet murdered human beings. He was a loner, yet kept the corpses of his victims in his flat for company. And despite the brutal way he slayed his victims, often cooking parts of their remains and boiling their heads before setting them on fire or flushing them down the toilet, he once said of his crimes: 'I can tell you what I did but I can't tell you why I did it.' A new documentary examining Nilsen's life and his crimes, due to be broadcast tomorrow on BBC Alba as part of a five-part series on Scotland's most infamous murderers, attempts to cast fresh eyes over the life of this serial killer, with a particular focus on his early days in Fraserburgh and Strichen.

• Dennis Nilsen Serial Killer Nicknames

Dennis Andrew Nilsen (born 23 November 1945, Fraserburgh, Scotland) also known as the Muswell Hill Murderer and the Kindly Killer is a British serial killer who.

'He skews opinion everywhere you go,' says executive producer Patsi Mackenzie. 'He doesn't fall into any particular psychological box, so it's tantalising subject matter because you can talk about him forever really. 'We thought it was worth looking at especially from a Scottish perspective. I don't think that his childhood has been covered too much in the past so it was good for us as Scottish programme makers to look at his early life in Fraserburgh.' Nilsen's Scottishness has often been played down. Along with Glaswegian Moors murderer Ian Brady, he is one of the few Scots we seem reluctant to lay claim to as our own. And because his crimes were perpetrated within London (he was known for a time as the Muswell Hill Murderer) and he is held in HM Prison Full Sutton in Yorkshire, many are unaware he is Scottish at all.

Yet it is his early life in Aberdeenshire that provided – or so Nilsen himself claims – the psychological trauma that marked him out as a murderer later in life. Born to a Scottish mother and a Norwegian father the year the Second World War ended, Nilsen's family life was rocky from an early age. When he was just four, his father, apparently a drunkard, walked out leaving him without a male role model. Instead, he came to idolise his grandfather, Andrew Whyte.

But when Whyte died two years later, it had a profound effect on Nilsen. Not only had he lost the only father figure in his life, but his mother forced him to view his gran father's dead body without telling him beforehand what he would be doing. Nilsen claims that the incident triggered a profound sense of loss and a lifelong fascination with corpses. It was not the only one. At the age of eight, Nilsen nearly drowned and was revived by an older boy who exhibited sexual interest in him.

This, Nilsen has claimed, impacted on him so much that his 4,000-page autobiography, which he has attempted unsuccessfully to have published several times, is entitled Memoirs of A Drowning Boy. Mackenzie is sceptical as to just how much of an impact these incidents may have had. 'It's open to interpretation,' she says. 'It's said by some that he has greatly embellished an awful lot of what happened. How much actually took place and how much was in his imagination – obviously nobody knows that but him.' By the time Nilsen was jailed in 1983 he had killed at least 15 men. Working in a London job centre after 11 years as a cook in the army, he lured his victims, most of them homosexual men he picked up in gay bars, to his homes in north London, his first in Cricklewood, and his second in Muswell Hill.

There he would strangle them with a tie, and often drown them as well, before keeping their corpses in his bed or on a chair for company. Then he would cut them up, keeping parts of the remains in different areas of the flat, and several of them under the floorboards. Some parts were burnt, others were flushed down the toilet. Occasionally he would boil their heads. Brian Masters, who wrote Killing for Company, the definitive biography of Nilsen, describes him as 'mad in his soul. He can make a cup of coffee and eat a slice of toast with the head of somebody bubbling a few inches away. If madness is anything, that is it.'

When Nilsen's crimes were finally uncovered, after drain cleaning company Dyno-Rod was called to his building in Muswell Hill to investigate a blocked drain and found human flesh, his cold confession shocked even the most hardened policemen. Former detective Peter Jay, who arrested Nilsen, still remembers the experience: 'You are sitting with him in your office and you are just looking at him in disbelief all the time. Because what he was telling us he'd done did not seem to go with the man who was sitting there.' One of those interviewed in the documentary is Betty Scott, Nilsen's mother, now 88 years old, who still lives quietly in Fraserburgh. Her life has been overshadowed by the acts of her son. 'I am always thinking about Dennis,' she says. 'Whenever I go through to my bed and I think about things from the past, Dennis is always there.'

She says the nature of her son's crimes still horrify her. 'I could not believe he had done that. Seeing the person growing up and seeing him admit that was like two different people.' And she says she's haunted by thoughts of the victims' families.

'I always think about them – how they must feel. I have always thought about the families and what they've gone through because of what Dennis had done.' She also talks about how overwhelmed she felt at the time by the press attention. 'I had all the newspapers but that didn't bother me. It was my son I was interested in, not them.' 'I think she's become accustomed, over the years, to press coverage and I'm not sure it's always been a good experience for her,' says Mackenzie.

'But there was no way I would have gone ahead without approaching her because it's her son and her life is directly affected by it.' Psychologists are still split over Nilsen, who remains in prison in Yorkshire, a rapidly ageing man who turned 64 yesterday, with no chance of parole. Some claim that he knew what he was doing, others believe he was entirely insane, or affected by the heavy amount of alcohol he was imbibing at the time of the crimes. But whether he is sane or not, there is still the question of why, so many years on, we continue to find an individual like Nilsen so fascinating. In the past, Nilsen has made his own opinion on other people's curiosity about his life clear. 'I am always surprised.

That anyone can be attracted by the macabre,' he said. 'Their fascination with types. Like myself plagues them with the mystery of why and how a living person can actually do things which may be only those dark images and acts secretly within them.' 'I think it's a psychological fascination,' concludes Mackenzie.

'You can dismiss these things and say they're just too horrible to contemplate, let's forget about it, lock them up and throw away the key and not face it. (But I think it's much better to accept that whether we like it or not, these things do happen in life, and to ask why. ' People like him are incredibly rare and so you want to ask that question.' • Dennis Nilsen – In Love With Death? Is on at 9pm on Wednesday 25 November on BBC Alba.

Dennis Nilsen was convicted in 1983 of six murders and two attempted murders HIS LIFE & CRIMES 1945 Born in Strichen, near Fraserburgh, on 23 November to a Scottish mother, Betty Scott, and a Norwegian father, Olav Magnus Moksheim, who adopts the surname Nilsen. 1949 Parents divorce.

1951 Nilsen's beloved grandfather dies and his mother, a strict Roman Catholic, demands he view the body. Nilsen later claims this incident scars him for life. 1961-1972 Joins the British Army and becomes a cook in the Catering Corps. Serves in South Yemen, Cyprus, Germany and the Shetlands.

1972 Leaves the army and serves briefly as a police officer before joining the civil service and moving to London. 1978 Kills his first victim, Stephen Dean Holmes, on 30 December by strangling him with a necktie and then drowning him in a bucket of water.

1979-1983 Kills an estimated 15 victims, some of whom have never been identified, many by strangulation and drowning. He often dismembers his victims after death, eventually burning them or flushing them down the toilet.

1983 Nilsen is arrested in February after dismembered flesh is found in the drains of his Muswell Hill home. 1983 Sentenced to life imprisonment on 4 November 1993 Gives a televised interview from prison. 2003 Brings a judicial review over a decision not to allow him to publish his autobiography, The History of a Drowning Boy. He is awaiting an appeal on this decision at the European Court of Human Rights. 2006 Denied any further requests for parole.

Advertisement Dennis Nilsen, a serial killer with a lot of twists, will be featured on the Voice Of A Serial Killer documental series on CBS Reality. Nilsen used to be a policeman and a butcher prior to that, so he put the skills he received from working in these positions to use in his sinister crimes, eventually becoming one of most horrifying murderers London has ever seen. The monster used a typical scenario to lure his victims, all of them young male gays. He used to seduce them to come to his apartment, where he would torture, kill and dismember them, after which he would hide the remains under the floorboards. When the smell of the rotting bodies became too strong, he would bury them in his garden, which eventually turned into a cemetery. Dennis Nilsen managed to slaughter at least a dozen young men in a four-year period during the late 70s. He says that keeping their corpses inside provided him with a certain comfort, because he needed the company and he did not want them to leave in the morning. The most satisfying part for him was that he felt strong and powerful.

Dennis Nilsen Serial Killer Nicknames

Image Source: PA Dr. David Holmes commented on his crimes for the Voice of a Serial Killer series, and said that Nilsen was a true chameleon who managed to completely blend in with society, and that he was one of those people who made others feel at ease. According to the specialist, Nilsen was aiming to lure passive men, because he did not want a lot of interaction between him and his victim. He apparently liked the company of a pronate character in order for himself to feel dominant and stronger. The murderer used to go to Camden in North London to hunt for new victims. His attitude was friendly and he acted shy, which clearly worked well. When he eventually found who he was looking for, he got them back into his flat of horrors, where he executed them by drowning or suffocating, and then the creepiest part comes in – he would bathe and dress up the corpse after the murder. When the body would start decomposing, he would dismember it and either burry the parts in his garden of flush some of them down the toilet.

Image Source: PA The reason for his arrest was the last method of disposal he practiced. When the drainage system became clogged in February 1983, a cleaning company had to be contacted to take care of the problem. After the gruesome discovery, Nilsen was arrested, and police officers took him to London’s Hornsea Police Station. Upon initial interrogation he found it hard to remember how many people he had killed and wondered if there were 12, 15 or 16 in total. Disturbingly, he seemed to enjoy his new celebrity status of being a serial killer. At one point he dressed himself as a corpse and shared even the smallest details about his horrible crimes, which stunned the detectives who worked on the case. Advertisement Shockingly, Nilsen admitted that he fornicated some of his victims after he killed them.

The brutal murderer confessed that at one point he had 2 or 3 hidden bodies under the floorboards of the flat. With summer coming in, he was aware that the smell would be unbearable before long and he had to do something, so he thought about it for some time, eventually deciding that the smell would come from inside the body, the soft organs and intestines. Nilsen also told investigators that he had to be in a very drunken state to be able to cut the bodies into pieces, and while doing that he often got sick of it and threw up in the garden. He also explained that he used to cut plastic bin bags into sheets, on which he would put the body and chop it up. He planned everything and kept a straightforward routine. He proceeded to cut the head of every body first, before chopping the limbs. Next he removed the internal organs and scattered them in different locations.

A few of the heads he put in suitcases buried in his garden. Nilsen was tried and convicted for six confirmed murders. Later he confessed that he had killed more people. Some of his victim’s names are Stephen Holmes, William Sutherland, Martyn Duffey, Kenneth Ockenden and Malcolm Barlow. After his conviction, Nilsen spoke a lot to Professor David Wilson, who worked as a prison officer at that time.

According to the specialist, Dennis Nilsen was a true narcissist and unlike other brutal serial killers, he seemed a more deeply troubled man who lacked sense of humor. Another reason for the murders may be related to the tough childhood Nilsen had. He got bullied as a kid and did not have many friends. On top of that, he was already aware of his sexuality and that apparently shut him down even more. You can watch the full episode of Voice of a Serial Killer on 3rd of January on CBS Reality.