A man has been jailed for three years for the manslaughter of 21-year-old James Harris-Durkin, from East Sussex, in a fight at a Diamond Jubilee party.
Liam Smith, 26, of Thorndon Close, St Paul's Cray, south-east London, had admitted the killing and perverting the course of justice at the Old Bailey.
Mr Harris-Durkin, from Eastbourne, died from head injuries after the attack in Court Road, Orpington on 5 June.
The father-of-three had initially travelled to Orpington for a funeral.
Smith, who had also attended the Diamond Jubilee celebration barbecue on Monday 4 June, was also given a three-month concurrent sentence, less 160 days already spent on remand, for perverting the course of justice.
His partner Leanne Turner, 25, of the same address, was given a six-month suspended jail term and 200 hours community service after also pleading guilty to perverting the course of justice.
A post-mortem examination showed Mr Harris-Durkin died from a "deep brain bleed linked to blunt force trauma".
The emergency services were called to Court Road at 03:30 BST on 5 June to reports of a man collapsed in the road.
Mr Harris-Durkin was taken by ambulance to the Royal London Hospital, where he died that evening.
Police said during the party he had become involved in an altercation, which flared up again later when a fight broke out with Smith and he suffered fatal injuries from two punches.
Judge Peter Rook QC told Smith it was his "choice" to engage in the fight.
He said: "It was not just one blow but it was two blows.
"In those few seconds you deprived Mr Harris-Durkin of his most precious possession, life itself."
In a statement read out in court, Mr Harris-Durkin's mother, Penny, said her son was a "lovely boy who was full of life", "funny" and "down to earth".
She said: "I have been left with a void in my life and in my heart. As a family we will miss out on the best years of his life.
"He will always be in our hearts."