Four 17-year-old boys have been locked up for the “ferocious” killing of another teenager who gatecrashed a girl’s 16th birthday party.

Lewis Blackman, 19, was stabbed 13 times after being chased from a flat in Kensington, west London in the early hours of February 18 last year.

Following trials at the Old Bailey, three boys, who were 16 at the time, were found guilty of murder and a fourth of manslaughter.

Demario Williams, who played a “pivotal role” in the murder, was detained for at least 20 years.

Lawrence Nkunku-Linongi, who had a previous conviction for carrying a “Rambo-style knife”, and Paul Glasgow, were handed minimum terms of 18 years.

And Thierry Edusei, who had been on bail on suspicion of violent offences at the time, was handed 11 years for manslaughter.

Judge Anthony Leonard QC lifted reporting restrictions on the defendants’ identities as he sentenced them.

He said: “Whilst it has to be accepted Lewis Blackman was himself acting aggressively that night, he did not deserve to die.

“His mother described him as a fun, popular and compassionate person, good at sports and loved his music.

“It’s hard to comprehend the savagery, so plain to see in the CCTV footage, that was meted out by 16-year-olds.”

The court had heard how Blackman arrived uninvited at the party, which was being held at a flat rented for the occasion from Airbnb, after invitations were circulated on social media, particularly Snapchat.

The birthday girl hoped about 50 people her age would attend her party.

She was cautious to only invite guests from Hackney, east London, and avoid boys from Camden because of “history” between the groups from those areas.

But Blackman was among 10 people from the north west London borough who turned up.

The victim was armed with a knife and his friend possessed a firearm when they attempted to force their way into the party, the court heard.

CCTV cameras caught a larger group of party-goers, some also armed with knives, chasing Blackman along the residential streets of Earls Court before they caught and stabbed him repeatedly.

Blackman died at the scene, suffering multiple stab wounds, including two to the chest.

Jurors were told the group’s “crazed expressions” had been replaced by a “triumphant swagger” as they returned to the flat where the party was being held, “visibly excited”.

The judge said the murder was aggravated by the fact it was a “sustained and ferocious attack” while the victim was running away.

Investigating officer Detective Chief Inspector Mark Cranwell, of Scotland Yard, said: “There is no excuse for the violence that Lewis Blackman was subjected to.

“The group who attacked him, all of them teenage boys, acted with almost unimaginable ferocity by inflicting 14 stab wounds.

“To then be captured laughing and joking to themselves in apparent triumph as another young man lay bleeding to death is beyond comprehension.”

He added: “Now four young men will spend some of the best and most promising years of their lives in prison, when they could have been doing something positive and productive.

“Lewis’ family have been left grieving for the loss of a young life taken far too soon.”