Dennis Andrew Nilsen (born 23 November 1945) is a serial killer and necrophiliac, also known as the Muswell Hill Murderer and the Kindly Killer, who committed the murders of 15 young men in London, England, between 1978 and 1983.

Nilsen was born on 23rd November 1945 at 10 High Street, Strichen, Fraserburgh, Aberdeenshire, to a Scottish mother, Elizabeth (Betty) Duthie Whyte, and a Norwegian father, Olav Magnus Moksheim, who adopted the surname Nilsen. His father was an alcoholic and his parents divorced when he was four years old. His mother remarried and sent her son to his grandparents, but after a couple of years he returned to his mother. Nilsen claimed the first traumatic event to shape his life came about when he was a small child, when his beloved grandfather died of a heart attack in October 1951. His strict Catholic mother insisted that he view the body before burial. His mother and stepfather’s lectures on the “impurities of the flesh” helped shape him into what he was to become. Nilsen’s father moved back to Norway, where he died. Nilsen was a beneficiary of the estate.

In 1961, Nilsen left school and joined the British Army. He enlisted in the Army Catering Corps and became a cook in South Yemen, Cyprus, Berlin, Germany and the Shetland Islands. He served in the army for 11 years, earning a General Service Medal before being discharged, at his own request in November 1972. In December 1972, he joined the Metropolitan Police, and was posted to Willesden, London in 1973. Nilsen served eight months as a policeman before resigning. From 1974, Nilsen worked as a civil servant in a jobcentre in Denmark Street, in London. He was also active in the trade union movement, even going on other people’s picket lines in solidarity. In November 1975, Nilsen moved into a flat at 195, Melrose Avenue, Cricklewood, London with office worker David Gallichan, to whom he gave the pet-name ‘Twinkle’. Gallichan moved out in 1977.

He was involved in a series of superficial, transitory relationships with men, though they did not assuage his feelings of profound isolation and loneliness. Like Jeffrey Dahmer, he sought somebody “who wouldn’t leave”; that is, a corpse. Between 1978 and 1983, Nilsen is known to have killed 15 men and boys. The majority of Nilsen’s victims were homeless or homosexual men whom he would typically meet in bars or on the streets and lure to his home with an offer of food, alcohol or shelter. Once at Nilsen’s home, the victims were usually given food and alcohol, then strangled and drowned during the night. He used his butchering skills, which he gained from his time as a cook in the army, to help him dispose of the bodies. The bodies were not immediately dismembered, but were kept, sometimes for several months, in different locations in his home, usually under the floorboards. Nilsen later admitted to having engaged in sexual acts with the corpses of his victims.

Nilsen had access to a large garden when living at 195 Melrose Avenue, Cricklewood. He was able to burn many of the remains in a bonfire. Entrails were dumped over the garden fence to be eaten by wildlife. In October 1981 Nilsen moved several miles eastwards to an attic flat at 23 Cranley Gardens, Muswell Hill. Here he had no access to a garden and the flat itself had no floorboards. This meant that, as his murders continued, he found it difficult to dispose of the remains and had bin bags full of human organs stored in his wardrobe. Neighbours began to notice the smell. Three people were murdered at this address, and all were stored in cupboards and chests. Nilsen attempted to dispose of the bodies by boiling the heads, hands and feet to remove the flesh and by chopping the entrails into small pieces and flushing them down the toilet. This eventually blocked the flats’ drains.

Nilsen’s murders were first discovered by Dyno-Rod, a drain-cleaning company responding to a blocked drain. The company found the drain was packed with a flesh-like substance. The drain inspector then called his supervisor, but no assessment was made until the next day, by which time the drain had been cleared. This aroused the suspicions of the drain inspector and his supervisor, who immediately called the police. Upon closer inspection, some small bones and what looked like chicken flesh were found in a pipe leading from the drain, with rats feeding on them; the remains were passed to pathologist Professor David Bowen, who advised that they were human.

• Murder 1, Stephen Holmes: Nilsen’s first murder occurred on 30 December 1978. The victim was described by Nilsen as being an Irish teenager he estimated to be around 17. Nilsen met the youth in the Cricklewood Arms on the evening of 29 December before inviting him to Melrose Avenue. The following morning, Nilsen strangled him with a necktie until he was unconscious before drowning him in a bucket of water. In January 2006, the victim was identified as Stephen Dean Holmes, a 14-year-old youth who was last seen on his way home from a rock concert. In November 2006, Nilsen confessed to the murder of Holmes in a letter sent from his prison cell to the Evening Standard. Nilsen was not charged with the murder as the Crown Prosecution Service decided that a prosecution would not be in the public interest. On 11 August 1979, Nilsen burned the body of Stephen Holmes in his garden.

• On 11 October 1979, Nilsen attempted to murder Andrew Ho, a student from Hong Kong he had met in The Salisbury public house in St. Martin’s Lane. Although afterwards he confessed to the police about the incident no charges were brought and Nilsen was not arrested.

• Murder 2, Kenneth Ockendon: Nilsen’s second victim was 23-year-old Canadian student Kenneth Ockendon. Nilsen met the tourist in a pub on 3 December 1979 and escorted him on a tour of Central London, after which they went back to Nilsen’s flat for another drink. Nilsen strangled him with the cord of his headphones whilst Ockendon was listening to a record. Ockendon was one of the few murder victims who was widely reported as a missing person.