A gunman was jailed for at least 28 years on Thursday for the murder of a former boxing champion who had asked a group of men to stop smoking in a bar.

Kanyanta Mulenga, 23, was given a life sentence at the Old Bailey after being found guilty of killing James Oyebola, 46, in Fulham, west London [Images], in July 2007.

"This was nothing short of a brutal killing carried out for the most trivial of reasons," judge Peter Rook said, according to the Press Association.

Oyebola, who was shot in the neck and leg, died in hospital four days after the shooting when doctors switched off his life-support machine.

The father of three had been asking people to stop smoking in the garden area of the bar, which counted as enclosed premises because it had a retracting roof.

Police said Mulenga and his friends "sauntered away from the scene" after the shooting, with one of them grabbing a bottle of vodka from the bar on their way out.

"The defendant chose the cowardly option of pulling a gun on James over something as minor as smoking a cigarette," said Detective Inspector Steve Horsley, of the Metropolitan Police, who led the investigation.

In a statement, Oyebola's family said the killing was "pointless" and had changed their lives.

"The late great Dr Martin Luther King Jr. once said 'Let no man pull you low enough to hate him'.

"We do not hate this young man found guilty; on the contrary we feel sorry for both him and his family," the statement said.

Oyebola won the British heavyweight title in 1994 and the bronze medal at the 1986 Commonwealth Games [Images] in Edinburgh, where he lost to Lennox Lewis in the semi-finals.

Rene McKoy, 20, of Battersea and Dean Francis, 24, of Wandsworth, both southwest London, who were in the bar with Mulenga, were cleared of murder after agreeing to give evidence for the prosecution.

A fourth man, who cannot be named for legal reasons, will face a separate trial.