A 36-year-old man has been found guilty of murdering a fellow train passenger following a row about whether he was blocking the aisle.
The court heard how Pencille, of no fixed abode, launched an “unrelenting” and “savage” attack on the unarmed and defenceless Mr Pomeroy, in front of dozens of other passengers.
The defendant had admitted carrying a knife but denied murder, claiming he had acted in self defence.
But after deliberating for almost 20 hours the jury found him guilty. He has now been sentenced to life, with a minimum term of 28 years.
Detective Chief Inspector Sam Blackburn, from British Transport Police, said after the conviction Pencille was “devious and dangerous”.
The trial had heard how Pencille had a history of violence, having previously stabbed a flatmate in the neck after a minor disagreement in 2010.
He also threatened to kill a staff member at a mental health hostel last year.
Pencille, who has been diagnosed with paranoid schizophrenia, has been seeing psychiatrists since 2004 but had not taken any anti-psychotic medication at the time of the attack on the train.
“He’s a dangerous man. Quite clearly with his previous convictions, where he also stabbed another man in the neck, and his propensity for carrying knives, he showed his dangerous, aggressive nature and that he wasn’t afraid to use that knife on that train on 4 January,” DCI Blackburn said.
The deadly row began when Pencille accused Mr Pomeroy and his son of blocking the aisle on the train in January.
Pencille was heard to swear at the 51-year-old IT consultant, call him a “pussy” and tell someone on his phone he was going to “kill this man”.
Mr Pomeroy demanded an apology but as he remonstrated Pencille swung his knife up and plunged it into the father’s neck, severing his jugular.
Prosecutor Jake Hallam QC had told jurors: “Eyewitnesses saw what they thought was the two men trading punches. They were half right.
“They saw Lee Pomeroy punching the first defendant, defending himself, having been stabbed in the neck by him.
“But the first defendant wasn’t punching back, he was stabbing. Again, and again, and again.”
Leaving Mr Pomeroy fatally wounded with 18 knife injuries to the neck, torso, thigh and arm, Pencille got off at the next station and was picked up by his girlfriend, Chelsea Mitchell.
The 28-year-old Mitchell also bought hair clippers and razors to help her partner change his appearance.
But less than 24 hours after he had knifed Mr Pomeroy to death, he was arrested by armed police after they raided Mitchell’s flat.
The girlfriend, from Farnham in Surrey, was also found guilty of helping Pencille evade police after the attack.
DCI Blackburn said he had no sympathy for Mitchell, who was blinded by her love for the killer.
“She did not want him to be captured. She did and still does have a love for Mr Pencille, which obviously blurred her mindset in relation to what she was doing.
“But she wanted him to remain free and she refused to accept what he had done was wrong.”
The bloodstained scene of the murder was the most “horrific” thing he had seen in his police career so far, the detective added.
“It’s devastated not only Lee’s mother, wife, sisters and obviously ... the son.
“But that has had a devastating effect on them [and] I hope they can start to rebuild their lives following this verdict.”