Fingers were found in a manhole as snow fell on a residential street.
The "smell of death" greeted police when they investigated the top floor flat in the semi-detached house above.
Black binbags of human remains sat in a wardrobe, with more to be found in the tea chest and bathroom, finally exposing the killer of 16-year-old Birkenhead boy, Martyn Duffey.
READ MORE: 'Upstanding' businessman mutilated victims for fun in spate of killings
Martyn was sleeping rough in Euston Station after hitchhiking from Birkenhead to London.
But the catering student didn't return home to his family.
In a heartbreaking documentary in 2020, his siblings Hazel and Graham spoke of their pain at not knowing where he was, saying: "He disappeared in front of our eyes."
They said : "Dad was relentless in his search for Martyn, he had his picture on his bedside and he always looked at his picture and said 'where are you son?'"
Unbeknown to them, Martyn's body was beneath the floorboards of Dennis Nilsen's house at 195 Melrose Avenue in London.
Nilsen is believed to have encountered Martyn while he was sleeping rough at Euston Station on May 17, 1980, as the killer returned from a union conference in Southport.
The murderer lured Martyn back to his flat with the promise of food and a bed for the night.
Instead of giving him comfort, Nilsen strangled the sleeping boy, subsequently drowning him in the kitchen sink.
He then bathed with the body, which he later described as "the youngest looking I had ever seen", using it for sexual activity before storing it in a cupboard for two days.
The killer moved the boy's body under the floorboards after spotting signs of bloating.
Martyn was the third known victim of the murderous Nilsen, born in Scotland in 1945.
The Birkenhead boy's siblings later revealed what his murderer did with his possessions.
They said : "He took a left luggage from Martyn and went to Euston to get his briefcase, he used Martyn's briefcase to take his sandwich to work in.
"He also took Martyn's chef knives that had been a present from our dad, and he used the chefs' knives to cut the victims up, that was a shock."
The first murder
Dennis Nilsen's murder spree started with 14-year-old Stephen Dean Holmes in December 1978.
The former soldier and police officer met the boy in a local pub where Stephen had been refused booze on his way back from a pop concert.
Nilsen offered him alcohol back at his Melrose Avenue flat.
Waking the next morning to the see the sleeping boy next to him, Nilsen strangled him to unconsciousness with a tie before drowning him in a bucket of water.
Nilsen washed Stephen's body before laying beside it in bed, and storing it beneath the floorboards for eight months, taking it out to pleasure himself.
Writing about the first murder, Nilsen said: "I had started down the avenue of death and possession of a new kind of flatmate."
He continued this ritual with his later victims, at least 15 of them, many unidentified.
At Melrose Avenue, he would burn the bodies on bonfires in the garden, grinding the bones once the flesh was burned off.
When police investigated the site after his arrest in 1983, they found hundreds of charred bone fragments.
A second victim
Almost exactly a year after the first murder, and following a failed attack on a student from Hong Kong, Nilsen found his next target.
Canadian student Kenneth Ockenden met Nilsen at a West End pub in December 1979.
With the promise of food and drink, Nilsen lured the 23-year-old back to his home where he strangled him with his headphone wire as he listened to music.
Nilsen then listened to music with the very same headphones, and watched TV for hours with Kenneth's body beside him.
He placed Kenneth under the floorboard, but he would bring his body back up in the following two weeks to take it to bed, photograph it in suggestive positions, and place it in his armchair as he drank.
Picking up the pace
The rate of Nilsen's murders escalated after Martyn Duffey.
He killed five more men and boys in 1980, having sex with some of them.
Only one, William Sutherland, 26, was ever identified.
The stench of rotting flesh filled the flat as the space beneath the floorboards ran low.
With flies buzzing around his home, Nilsen took to cutting up his victims with Martyn's knives, and boiling some of their heads in water to remove the flesh.
He buried limbs in the back garden of Melrose Avenue, and stuff body parts in suitcases until time came to burn them.
One last man was to die at this house before Nilsen was forced to leave by his landlord.
Malcolm Barlow, 23, visited Nilsen to thank him for calling an ambulance when he suffered a epileptic seizure outside Nilsen's home.
But the murderer strangled the young man, stuffing Malcolm's body under the kitchen sink.
23 Cranley Gardens
Nilsen burned the bodies of his final five Melrose Avenue victims before moving on to Cranley Gardens in Muswell Hill, North London.
Without a back garden, disposing of his victim's bodies became more difficult.
Three more men were to die at Cranley Gardens, their bodies violated and dissected by Nilsen for his sadistic pleasure.
Nilsen dismembered his last three victims - John Howlett, 23, Graham Allen, 27, and Stephen Sinclair, 20 - boiling their body parts so their flesh dissolved.
He tried to flush the remaining internal organs and small bones down the toilet, which became his downfall.
The drains clogged, forcing a rancid smell up the nostrils of every resident in the building.
Nilsen and others living their reported the smell and drainage issues, leading to two men from Dyno-Rod, an emergency drainage and plumbing company, to inspect the manhole at the side of 23 Cranley Gardens.
There they saw what looked like flesh, being chewed upon by rats and maggots.
Alarmed at the sight, they called police, who investigated the drain that was being blocked by human remains originating in the top floor flat where Dennis Nilsen lived.
There they found body parts in bags and cupboards all over the killer's home, and his murder spree finally came to an end after five years.
Nilsen was convicted of six counts of murder and two attempted murders on November 4, 1983, for which he was sentenced to life in prison.
He died in 2018 after spending 35 years in prison.
Speaking of the horror of Nilsen's crimes, Martyn Duffey's siblings said: "Something like this can tear families apart, but this brought us together, Martyn was part of our family he was loved and we miss him."
