By ITV News reporter Sejal Karia
Serial killer Stephen Port, who has been found guilty of murdering four young men, duped police for over a year as he committed his killing spree.
He secretly drugged his victims, whom he found through dating apps, to indulge in a fetish for sex with unconscious men and then dumped their bodies yards from his flat.
The 41-year-old chef was convicted at London's Old Bailey of 22 offences against 11 men, including the four murders.
His victims were Anthony Walgate, Gabriel Kovari, Daniel Whitworth and Jack Taylor, all of whom were plied by Port with fatal doses of the date-rape drug GHB.
But it took the Metropolitan Police some 15 months to link the men's deaths and catch their killer.
Video shows the locations where the victims were found close to Stephen Port's home
The sisters of Port's final victim, Jack Taylor, believe he should have been caught earlier.
Donna Taylor told ITV News, "Had (the Metropolitan police) done their jobs properly Jack would still be here.”
Anthony Walgate was Port's first victim in June 2014, and the first to attract the police's attention.
He was a 23-year-old fashion and design student at Middlesex University, but also a part-time male escort.
Port had hired Mr Walgate and invited him to his home, before secretly overdosing him with GHB and dumping his body outside the block of flats where he lived in Barking, Essex.
He then made a 999 call pretending he had come across the body while out driving. He told the operator: "There's a young boy. Looks like he's collapsed outside. Looks like he's collapsed or had a seizure or something or is just drunk."
When the operator asked Port for his number he had already hung up. The operator had to call back to ask if the person was breathing.
When the paramedic eventually arrived he found Mr Walgate's body with 14 separate injuries which included grazes and bruising to his inside upper left arm.
Police officers tracked Port down to his flat through his telephone number. They noted him as a witness and took his statement.
Officers later realised Port had hired Mr Walgate as an escort and had been lying about the events of that night. They arrested him and Port was eventually jailed for perverting the course of justice in connection with Mr Walgate's death.
But detectives failed to investigate Port over Mr Walgate's killing, and in the intervening period before he went to prison he went on to murder another two men.
While on bail, Port killed Slovakian national Gabriel Kovari, 22, in August 2014.
Three weeks later, Daniel Whitworth, a 21-year-old trainee chef from Gravesend, Kent became the killer’s third victim.
Both men's bodies were dumped in the same spot at a churchyard, 400 metres from Port's flat. The murder trial heard there was evidence to suggest they had been dragged there.
But Port went further, placing a fake suicide note on Mr Whitworth's body, claiming responsibility for Mr Kovari's death.
"I took the life of my friend Gabriel,” he wrote in the letter, adding: "Please do not blame the guy I was with last night."
That "guy" was Stephen Port.
The jury was told the letter was initially taken at face value by Scotland Yard officers and not investigated.
The killings stopped while Port served his sentence for lying about Mr Walgate's death. He had been sentenced to eight months, served half and was then freed on licence.
After his release, Port killed his fourth and final victim, Taylor, a 25-year-old forklift driver from Dagenham, Essex. CCTV captured him walking with Port in the final sighting before he was murdered.
At the time, Mr Taylor's sisters refused to accept the police's explanation of how their brother died. Officers told them he had died from a self-induced drugs overdose.
They felt something was not right and began their own investigation trying to piece together the last hours of his life based on their suspicions. But the police remained unconvinced.
"It felt like we were doing the police job, that's how it felt," Jenny Taylor said.
Sister Donna Taylor said: "We were up till five, half five every morning, started off with one sheet of A4 and ended up with probably about 100 ... of just different bits we'd found but we weren't sure where they went ... if they definitely connected."
She added: "We didn't know what we were searching for but we were trying to put the puzzle together for it to make sense and then we went online and found that there were other people who'd passed away very close to where Jack was found so we questioned the police over that and they told us there was no links and we just kept pushing."
The Metropolitan Police and 17 of its officers involved in the initial part of the case are now under investigation by the police watchdog, the Independent Police Complaints Commission.
Senior Officers said they could not offer an apology to the victim's families, for what it describes as "missed opportunities" in the case, until the IPCC inquiry was over and it required them to do so.
Commander Stuart Cundy from Metropolitan Police said: "An independent investigation will very much go to the heart to understand whether those missed opportunities required the Met to offer an apology to the families."
He added, "If there are lessons to be learned from what the IPCC find out then clearly the Met will carefully consider them and definitely learn from them."
Mr Taylor's sisters said they had lost faith in the police.
"Stephen Port may have done what he's done to Jack but if (the police) had done their job properly Jack would still be here,” said Donna Taylor.
“I will take that with me for the rest of my life, we all will."