A rail passenger was stabbed to death in front of his teenage son by another traveller who accused him of blocking the aisle, a court has heard.
Lee Pomeroy, 51, was knifed 18 times after getting into a row with 36-year-old Darren Pencille on board the Guildford to London train on January 4, the Old Bailey was told.
After attacking the father of one, Mr Pencille, allegedly fled at the next station and was picked up by his girlfriend Chelsea Mitchell, 27, who is accused of buying hair clippers and razors in order to help him change his appearance.
Opening the case against him, prosecution barrister, Jake Hallam QC, described how the initial exchange between the Mr Pomeroy and his alleged attacker had been "fast moving, unexpected and tragic".
He said Mr Pomeroy had been killed the day before he was due to celebrate his 52nd birthday.
At 1.01pm on Friday January 4, Mr Pomeroy and his son boarded a train at London Road station in Guildford bound for London Waterloo.
Mr Hallam told the jury: "He did not leave it alive. Within five minutes of boarding that train, Lee Pomeroy had been stabbed in the neck by the first defendant, Darren Pencille.
"It was the first of 18 knife wounds that he inflicted upon him.
"A little over an hour after he boarded the train, and despite the best efforts of the emergency services who rushed to save his life, Lee Pomeroy was dead."
He explained that Mr Pomeroy and his son had boarded the train via different doors to Mr Pencille, but they had ended up in the same carriage.
Mr Hallam suggested that the father and son may have been "blocking" Mr Pencille's way, prompting the snide response: "Ignorance is bliss."
Mr Pencille allegedly made the comment twice, prompting Mr Pomeroy to ask what he meant, precipitating a "heated" row.
Mr Pencille allegedly shouted: "You touch me, you touch me and you see what happens at the next stop."
Witnesses told police that Mr Pomeroy had demanded an apology from his alleged attacker saying : "You should not have humiliated me in front of my kid."
Another witness claimed Mr Pencille had accused Mr Pomeroy of being racist, even though he had not used any racist language.
Mr Pencille then challenged his alleged victim, telling him: "Listen, right. I dare you, I dare you. I dare you. Put your hand on me. Put your hand on me cos it won't end nicely. Put your hand on me."
Seconds later, Mr Pomeroy was stabbed in the neck, the court heard.
Mr Pencille, of no fixed address, denies murder and Miss Mitchell, of Farnham, Surrey, has pleaded not guilty to assisting an offender.
The trial continues.