A "unpredictable and dangerous" man who used a sword to kill a kickboxer at a party has been jailed for life.
Dainius Kasiliauskis, 27, was attacked at an address at Tilton Court, Peterborough on 12 June.
Leam Smith, 19, of Branston Rise in the city, was found guilty of murder at Cambridge Crown Court and must serve a minimum of 17 years.
Alvaro Vilhete, 30, of no fixed address, was convicted of assault and sentenced to seven years in prison.
Smith claimed he "leapt to the defence" of class A drug dealer Vilhete, when he attacked Mr Kasiliauskis, who he knew was a trained fighter.
The trial heard the Lithuanian national was a regular drug user and had been refused them by Vilhete.
The court was told Mr Kasiliauskis punched the drug dealer, who then produced a hammer and struck him.
A woman at the party then produced a sword "in an attempt to calm things down".
Smith then took the weapon and fatally stabbed the father-of-three several times, the court heard.
In statement read in court, the mother of the victim, Rasa Kasiliauskiene, said her only child "had the best heart and most caring attitude towards anyone".
Defence barrister Lisa Wilding QC said Smith had ADHD and learning disabilities and the attack was "entirely spontaneous".
Judge David Farrell described him as a "highly unpredictable and dangerous" man who used "a particularly vicious weapon".
The judge told Valhete, who was cleared of murder, that he had attacked an unarmed Mr Kasiliauskis in a "sustained and repeated assault".
Smith also pleaded guilty to two separate offences, a robbery and an assault, related to an attack carried out with another man at Welland skate park in the early hours of Saturday, 6 June.
Leon Holmes, 20, of Wentworth Street, also admitted robbery and assault and was jailed for six years.
Cambridgeshire Police said a video of the skatepark attack was shared by Holmes on Snapchat.