Media playback is unsupported on your device Media caption The BBC's Daniel Sandford reports on the crimes of Stephen Port, "a serial rapist who became a serial killer"

A serial killer has been found guilty of murdering four young men by poisoning them with lethal doses of a date rape drug.

Stephen Port, 41, lured his victims to his London flat and secretly gave them GHB, the Old Bailey heard.

Scotland Yard believes there could be more victims and is reviewing 58 deaths in London spanning four years involving the drug.

Port, who denied 29 charges, will be sentenced on Friday.

The chef was also found guilty of 10 offences of administering a substance with intent, four rapes and four sexual assaults.

Image copyright Stephen Port/Met Police Image caption Port presented a very different version of himself online (left) where he claimed he'd been in the navy and graduated from Oxford University

Between August 2014 and September 2015, Port murdered Gabriel Kovari, 22, from Lewisham, Daniel Whitworth, 21, from Gravesend, Kent, and Jack Taylor, 25, from Dagenham, east London.

The jury also found him guilty of murdering Anthony Walgate, 23, from Dagenham, in June 2014 by a majority verdict.

Port met his victims on dating websites, including Grindr, and coaxed them to his home in Barking for sex before giving them fatal doses of drugs.

Their bodies were all found dumped in or near a graveyard within 500m of his house.

How did police miss killer Stephen Port?

The Metropolitan Police admitted it missed "potential opportunities" in investigating the deaths and has urged any other victims to come forward.

The force's own LGBT independent advisory group and journalists from the website Pink News had raised concerns about a serial killer being at large but were told the deaths were unconnected.

The Independent Police Complaints Commission is currently investigating how the force handled the initial investigation into the deaths.

Seven officers have been served with gross misconduct notices advising them their conduct is under investigation. Another 10 have been served with misconduct notices.

Cdr Stuart Cundy, from the Met, said he was personally writing to the victims' families "to express our sincere condolences".

Image copyright PA Image caption Port murdered the men at his flat in Barking, east London, before dumping their bodies in and around a nearby graveyard

Port was found not guilty of three rapes relating to two living complainants.

The trial had heard he had an insatiable appetite for boyish-looking, smaller men, who he referred to as "Twinks".

Media playback is unsupported on your device Media caption In a police interview in 2015, Port tried to implicate Daniel Whitworth in the death of Gabriel Kovari

The Old Bailey was also told he trawled the internet for pornography involving impassive young men being "raped" by older men.

Home videos were played to the jury of 10 women and two men which appeared to show Port allegedly enacting his drug-rape obsession.

At court: Danny Shaw - BBC Home Affairs Correspondent

As the 12 jurors took their seats, there was an almost palpable sense of tension.

Every day since Monday of last week, when the jury's deliberations began, relatives of Port's victims have gathered waiting for the outcome of this harrowing case.

At 10:35, the jury forewoman was asked whether they'd reached unanimous verdicts on each of the counts and, if so, what that verdict was.

When the first reply of "guilty" came back Port just sighed.

But to his right, there were sobs, tears and hugs among the parents and siblings of those who were murdered.

The murders

Image copyright Met Police Image caption Anthony Walgate (left) and Gabriel Kovari were Port's first victims

Anthony Walgate occasionally worked as a male escort and met Port when he offered the 23-year-old student £800 for an overnight date.

Mr Walgate had told a friend about the date "in case I get killed" but was found dead outside Port's flat on 19 June 2014.

Port later admitted he had "panicked" over the death and was jailed for perverting the course of justice, but he continued to claim Mr Walgate died from taking his own drugs.

Image copyright Met Police Image caption Daniel Whitworth (L) was murdered a year before Jack Taylor (R) died

Gabriel Kovari was staying with Port as a temporary flatmate when he was killed in August 2014.

Port called his sister to confess he had his body in his bed then dragged the 22-year-old to a nearby graveyard.

He then constructed a web of deceit to divert suspicion, telling his neighbour that Mr Kovari had died of an infection in Spain.

Port also invented a Facebook identity via which he told the Slovakian's boyfriend Mr Kovari had gone to a sex party with a man named "Dan".

Image copyright Met Police Image caption The suicide note, written by Port, sought to absolve him of any part in Mr Whitworth's death

The same dog walker who found Mr Kovari's body also found Daniel Whitworth dead in the same spot in the churchyard and "lying in the exact same position" three weeks later.

A fake suicide note was found in his hand which purported to be a confession by Mr Whitworth for Mr Kovari's death.

It was later found to have been written by Port but at the time of Mr Whitworth's death police had treated his demise "at face value".

Image copyright PA Image caption Mr Kovari and Mr Whitworth's bodies were found in the graveyard of St Margaret's Church

Jack Taylor died on 13 September 2015, hours after meeting with Port. The pair had earlier shared a conversation on Grindr.

Following his murder, Port disposed of Mr Taylor's mobile phone and deleted their communication on the dating app.

His body was found by a refuse collector with a needle and syringe in his pocket.

Image copyright AFP/NIKLAS HALLE'N Image caption Jack Taylor's family gave their reaction to Port's conviction at the Old Bailey

Speaking outside court following the verdicts, Daniel Whitworth's family said they were still "bereft at the loss of a such a clever, talented and much-loved boy".

His step-mother, Mandy Pearson, said the guilty verdict "has marked the end of a large part of our battle" but the family "have yet to concentrate on other areas of accountability".

"The fight goes on until all our questions are answered," she said.

Jack Taylor's family said they felt he would still be alive if the police "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," they said.

Image copyright AFP/ NIKLAS HALLE'N Image caption Mr Whitworth's family made only passing reference to the initial police probe of his death

Police believe there are many other victims and have urged people to come forward.

As Port used a variety of social networks and dating apps to meet men, the Met has released a list of his account details in a bid to aid any other possible victims.