Police faced a storm of criticism as serial killer Stephen Port was found guilty of murdering four young gay men to fulfil his depraved sexual fantasies.
The 41-year-old chef stalked his victims on dating websites and plied them with drinks spiked with fatal amounts of drug GHB to rape them while they were unconscious.
He dumped their bodies in or near a graveyard within 500 metres of his flat in Barking, east London, and embarked on an elaborate cover-up.
He disposed of their mobile phones, repeatedly lied to police and planted a fake suicide note in the hand of one of his victims, taking the blame for the death of another.
Following an Old Bailey trial, Port was found guilty of the murders after a jury deliberated for 28 hours and 27 minutes. He could face spending the rest of his life behind bars.
The deaths of Jack Taylor, Anthony Walgate, Gabriel Kovari and Daniel Whitworth over 15 months bore striking similarities but police allegedly failed to make the link until relatives of his final victim demanded answers.
Mr Taylor's family, who are planning to sue, said: "We do believe Jack would still be here if they had done their job.
"The police should be held accountable for Jack's death. We do understand it's not them who took Jack's life, but Stephen Port would have been stopped."
The family refused to accept Mr Taylor would have taken drugs willingly and put pressure on officers to treat his death as suspicious.
Human rights campaigner Peter Tatchell said: "While timely and commendable, this verdict is no compensation for the loss of four young gay men who had their lives, hopes and dreams cut short."
He accused the police of "class, gender and sexuality bias" and said lives would have been saved if police had acted on concerns sooner.
He said: "If four young well-off women had been murdered in Mayfair, I believe the police would have made a public appeal much sooner and mounted a far more comprehensive investigation."
An Independent Police Complaints Commission inquiry is ongoing into the handling of the case and 17 officers are facing investigation into possible misconduct.
Family quietly cheered as Port was found guilty of murdering Mr Walgate by a majority of 11 to one.
Port's sentencing was adjourned until 10.30am on Friday.
The court heard Port had an insatiable desire for boyish-looking men he referred to as Twinks.
He trawled the internet for pornography involving inert young men being "raped" by older men.
The victims' relatives sat through harrowing evidence which included home videos of Port enacting his drug rape obsession.
The first victim, Mr Walgate, 23, was found dead in the communal hall of Port's flat in Cooke Street after he called 999 anonymously in the early hours of June 19 2014.
When police tracked him down, Port lied to officers to distance himself from the fashion student and occasional male escort.
He was later forced to admit he "panicked" over the death of the young man he had engaged for sex through Sleepyboys website.
He was later jailed for perverting the course of justice but continued to claim Mr Walgate died from taking his own drugs.
Second to die was 22-year-old Slovakian Mr Kovari, who was staying on Port's sofa as a temporary flatmate.
After killing him, Port spoke to his older sister Sharon on the phone and confessed he had a body in his bed.
But rather than going to police, he dragged the body to Barking Abbey graveyard to be discovered by a dog walker.
Port constructed a complex web of deceit, telling his neighbour that Mr Kovari died of an infection in Spain.
Over months, he posed on Facebook as an American student to probe Mr Kovari's grief-stricken Spanish boyfriend and divert suspicion by suggesting the victim had gone off to a sex party with "Dan".
Prosecutor Jonathan Rees QC told jurors that the misinformation was to "lay the groundwork" for implicating his third victim, Mr Whitworth, even though Port maintained his story.
Three weeks after Mr Kovari was found dead, the same dog walker stumbled across the body of Mr Whitworth, 21, from Gravesend, on September 20, 2014.
In his hand, was a suicide note taking the blame for Mr Kovari's death, saying: "We was having some fun at a mate's place and I got carried away and gave him another shot of G."
It added a plea not to "blame the guy I was with last night" and an explanation that he had dropped his phone on the way.
Police treated Mr Whitworth's death "at face value" and no efforts were made to verify the sham note which turned out to be in Port's handwriting, Mr Rees told jurors.
Mr Taylor, 25, died within hours of hooking up with Port on Grindr in the early hours of September 13 2015.
After killing him, Port got rid of the forklift truck driver's mobile phone and deleted their communication on the gay dating app.
Just after 1pm the next day, Mr Taylor's body was found by a refuse collector with a needle and syringe in his pocket.
Initially, his death was treated as "non-suspicious", the court heard.
But CCTV footage from Barking Station emerged linking him to Port, whose DNA was found on a bottle of GHB also planted in Mr Taylor's trouser pocket.
Giving evidence, Port maintained his lying accounts and claimed he had left Mr Taylor "very much" alive after having "rampant" sex outside.
On why he lied to police, Port said: "The truth sounded like a lie, so I lied to make it sound like the truth."
However, the prosecution rejected his explanations as absurd, ridiculous and cruel to the families who deserved to know the truth.
Detective Chief Inspector Tim Duffield, who led the the Port homicide investigation and has been a police officer for 28 years, said: "Stephen Port is probably one of the most dangerous individuals I've encountered. He's a voracious sexual predator who appears to have been fixated, nay obsessed, with surreptitiously drugging young, often vulnerable men for the exclusive purpose of rape.
"From what we've seen as an investigation team, this is a highly devious, manipulative and self-obsessed individual. Throughout both the criminal investigation, many days of police interviews and during the course of a long trial, he has never once shown a shred of remorse for his victims or indeed their families."
Commander Stuart Cundy, from the Met's Specialist Crime and Operations command, added: "From the evidence we've heard at trial there were potential opportunities that were missed. The IPCC investigation will carefully consider those."
Nik Noone, chief executive of LGBT anti-violence charity Galop, said: "Our thoughts are with the friends and families of the young men who tragically lost their lives, the survivors that have come forward and those who are affected by the issues raised in this case.
"Our focus now turns to understanding what lessons need to be learnt from the police response to unexplained deaths and sexual assault of young men and what must be done to learn how to prevent someone like Port in the future."
Port stared at the floor as he was convicted of the fourth murder, but turned to look at the family in court as the guilty verdict was given.
The jury convicted Port of a total of 22 offences against 11 men, including the four murders, four rapes, 10 counts of administering a substance, and four sex assaults.
He was cleared on three counts of rape.
Police have not ruled out the possibility there may be more victims of Port's sexual abuse and appealed for them to come forward.
Mr Cundy said: "Now we have the verdict I am personally writing to each of the families of the four young men who died as well as Daniel Whitworth's partner to express our sincere condolences. The letters, which we are giving them today, apologise to them for those missed opportunities."