London (CNN) A serial killer who drugged and murdered four men he met on gay dating sites has been jailed for life.

Stephen Port, 41, from London, was convicted of killing Anthony Walgate, 23, Gabriel Kovari, Daniel Whitworth, 21, and Jack Taylor, 25, over a 15-month period between June 2014 and September 2015.

He was also found guilty of drugging or sexually assaulting seven other victims, who survived.

A judge at London's Old Bailey handed the killer a whole-life term, meaning he will never be released. "The defendant will die in prison," Mr. Justice Openshaw explained, as cheers broke out in the public gallery.

In his summing up the judge said Port had committed the murders " in the course of satisfying his lust " for young men whom he had rendered unconscious with drugs.

'Wicked and monstrous' cover-up

Port's attempt to cover-up two of the murders with a fake suicide note was, he said, "wicked and monstrous."

The judge said he accepted that Port intended to cause serious harm rather than death but said "he must have known and foreseen there was a high risk of death, the more so after the death of the first victim."

Port, a chef and part-time male escort, lured his victims to his flat using online dating sites, before plying them with drinks laced with lethal doses of the sex-enhancing drug GHB in order to rape them while they were unconscious.

He then dumped their bodies in or near a graveyard close to his home in Barking, east London, and proceeded to foil police with elaborate cover-ups, including deleting dating accounts and planting drugs on the bodies of his victims.

Familes 'devastated and broken'

Outside court, relatives of Port's final victim, who drove police to investigate the deaths, expressed their satisfaction with the verdict.

Jack Taylor's sister Donna said: "We finally have justice for Jack and the other boys. A sick and twisted scumbag will never be able to hurt or destroy any other family's life. Jack can finally rest in peace."

Stephen Port, 41, was found guilty of more than 20 offenses, including four murders.

The family are planning to sue the police for failing to properly investigate the earlier deaths of Walgate, Kovari and Whitworth. They believe their son, who was a forklift truck driver, would still be alive if they had linked the deaths and caught Port earlier.

Prior to the sentencing, in victim impact statements, Walgate's mother said her son's death had "devastated and broken the family," while Daniel Whitworth's father Adam said he had been given "a life sentence of grief."

Kovari's brother Adam spoke of the difficulty in telling their mother of his death, saying: "There is no pain greater than losing a child," and the Taylor family said they had "truly fallen apart" as a result of Jack's murder.

A sex attack victim, who cannot be identified, told the court he blamed himself for not reporting the assault sooner, saying that if he had spoke out, he might have been able to prevent Taylor's death.

Port was given a second life sentence for the rape charges and another ten years for administering drugs.

Cases dismissed as overdoses

In mitigation, Port's counsel said he had "descended into a vortex ... he graduated from a fetish to a fixation from a fixation to a compulsion."

The fall-out of the Port case is likely to continue: UK police are reviewing the chemsex-related deaths of 58 other men , previously dismissed as drug overdoses, amid fears some may be linked to Port.

And the UK's independent police watchdog has launched an investigation into 17 police officers for misconduct in the case.

Despite striking similarities in all four cases, police did not realize that a serial killer was at work.

Murder victim Jack Taylor seen on CCTV with his killer Stephen Port.

In the first case, Port left Walgate dead in his flat, and went to work. When he came home he proceeded to cover up his actions by dressing the body, putting a small bottle of GHB in Walgate's pocket, and dragging it outside. He then called an ambulance, claiming to have come across the corpse by chance.

Interviewed by police a second time, he changed his story to suggest Walgate had visited his flat but had died by giving himself an overdose. He said dragged the body outside so that the police would not suspect him of murder. Officers took Port at his word, and charged him with trying to pervert the course of justice.

"Whether the police were right to do so, in the light of what they knew or ought to have found out, is for others to decide, having thoroughly inquired into the matter," he said.

Port was convicted and jailed for lying to the police, but was freed months later to kill again.

He was eventually caught when police found CCTV footage of him with one of his victims at a local station, and his DNA was found on a bottle of GHB planted in Taylor's trouser pocket.

"These evil crimes have left entire families, a community and a nation in shock," said Detective Chief Inspector Tim Duffield, the senior investigator in the case.

"Port is one of the most dangerous individuals I've encountered in almost 28 years of policing and a full life-term in prison was the only appropriate punishment in the circumstances," he added.