A John Travolta fantasist will die behind bars for the "cruel and brutal" rape and murder of a teenage girl 34 years ago.
For half a lifetime, self-employed tiler James Warnock, 56, evaded justice for strangling 17-year-old Yiannoulla Yianni in her own home, just half a mile from where he lived in north London.
Police cracked the case by matching his DNA to the crime scene last year, after Warnock was caught by an undercover officer sharing indecent pictures of children on the internet.
The divorced father-of-two, who was still living in the local community, claimed he had a secret affair with Yiannoulla, even though the teenager was brought up in a traditional Greek Cypriot family and never had a boyfriend.
A jury at the Old Bailey took just over two hours to convict Warnock, and Recorder of London Nicholas Hilliard QC jailed him for life with a minimum of 25 years for murder.
The judge said Yiannoulla had endured a "terrifying ordeal" at knifepoint and was killed in a way that was "cruel, brutal and without mercy".
He said: "It is impossible to understand how one human being could do such things to another and in the process you visited misery beyond measure on those whom Yiannoulla was and is so dear and which will never leave them."
Warnock was also sentenced to 20 years for rape and a range of terms of between four years and five months after admitting six counts of distributing indecent images in 2013, all to run concurrently.
Paying tribute to Yiannoulla, the judge told Warnock that the "brightness of her spirit" meant that she would forever be remembered as a "happy and hopeful" teenager and not defined by "the awful things you did to her".
The defendant would continue to pose a risk to young women but is likely to die in jail, he said.
Warnock made no reaction as he was sent down.
The murder had shocked the nation and led to high-profile police appeals, with detectives travelling as far afield as Australia in their search for the killer.
Her brothers and sister, who had sat through the distressing trial, broke down in tears as they finally saw Yiannoulla's killer brought to justice.
The court had heard how on August 13 1982, the victim, known as Lucy, had been with her parents at their shoe repair shop minutes away from their Hampstead home.
Yiannoulla's mother, Elli, had sent her home to start preparing a leg of lamb for supper, saying she would join her soon.
She was playing the latest Patrice Rushen hit Forget Me Nots on the record player when Warnock knocked on her door at about 2pm.
The court heard that Warnock had stalked her before, and followed her home after spotting her around her father's shop.
Her parents arrived home half an hour later to "a sight beyond their worst imagining" - Yiannoulla's partially naked body lying on their bed, prosecutor Crispin Aylett QC said.
Despite a high-profile public appeal, including a televised reconstruction featuring her sister Maria, no real suspects were identified.
More than 1,000 people came forward with information but police were no closer to finding the doorstep stalker and the case remained unsolved for decades.
In efforts to keep the investigation going, her heartbroken father, George Yianni, appealed to then prime minister Margaret Thatcher and the commissioner of Scotland Yard. He never recovered from the grief and died in 1988 after contracting a brain tumour.
At the time of the murder, 5ft 6in Warnock was aged 22 and gave the impression of being a "cocky ladies' man", with his hair carefully salon-styled and blow-dried like his Saturday NightFever idol.
But when officers tracked him down after matching his DNA to the crime scene, they found the heavily tattooed, balding and portly defendant awaiting their arrival, drinking beer in his underpants.
In a police interview he was asked what he looked like in the 1980s and he said: "How can I put it? Er, John Travolta?"
During the trial, Yiannoulla's brothers and sister relived the nightmare of her violent death while her now 86-year-old mother was among those to give evidence.
They were even forced to listen as Warnock, formerly of Harrington Street in Camden, north-west London, maintained his claim that he used to go to their home to have sex.
Following the verdict, they described how the loss of their beautiful sister had left the family "saturated by grief" although they never gave up hope of finding the man responsible.
Her brother Rick said: "Thankfully the long arm of the law has reached out from the past to bring this evil being to justice."
Detective Inspector Julie Willats told how she was at the theatre last December when she received a text informing her of her "lucky break" in the case.
She said: "He must have known we would be coming for him. It's the science that has solved this one for us."
At the time of the murder, techniques in DNA testing had yet to be invented.
Aisling Hosein, CPS London reviewing lawyer, said: "More than three decades since this terrible crime, James Warnock has finally been brought to justice.
"I would like to thank Yiannoulla's family for their support of the prosecution and for giving evidence in court, which must have been a harrowing experience after 34 years.
"Warnock's continuing lies have only served to cause more pain to the family but I hope that his conviction today can bring them some small comfort.
"This conviction should send a strong message that people who commit such serious crimes can be brought to justice many years later and we are committed to working with our police partners to ensure that perpetrators are held accountable for their actions."