Omar Wilson, 31, headbutted and kicked Gordon Ramsay protege Mussie Imnetu, 41, outside Dr Power restaurant in West London.
CCTV showed Mussie, who was head chef at the Arts Club Dubai, leaving the restaurant's sister venue in Dover Street, Mayfair.
Sentencing, Judge Philip Katz said: "The footage was deeply shocking to watch; Mussie was defenceless on the ground when you punched him and kicked him to death.".
The charity worker also punched Mussie, who didn't lay a hand on the killer, five times in the head.
As lay collapsed and gravely injured on the ground, Wilson continued to attack the chef.
