An IT consultant on a day out with his son was stabbed 18 times and died following a row with a man on a train, a court has heard.

Darren Pencille, 36, is said to have knifed 51-year-old Lee Pomeroy in the neck during an argument on the Guildford to London Waterloo train on January 4.

Mr Pomeroy, who would have celebrated his 52nd birthday the day after the attack, was on his way to the capital for a day trip with his 14-year-old son.

The court was told the row is thought to have started when Pencille accused Mr Pomeroy of blocking the carriage's aisle.

Pencille called Mr Pomeroy a 'c**t' and a 'p***y' before the victim was heard telling him 'you shouldn't have humiliated me in front of my kid,' witnesses said.

He died on the platform at Horsley station a little over an hour later, with a wound to his neck, eight cuts to his torso and wounds to his arm, hands and thigh.

Lee Pomeroy was attacked and killed on a train from Guildford to Waterloo in January

Darren Pencille started arguing with Mr Pomeroy minutes after getting on the train, apparently over whether Mr Pomeroy was blocking the aisle

Prosecutor Jacob Hallam QC said Pencille denies murder and claims he was acting in self-defence.

Mr Hallam told jurors: 'On Saturday January 5, Lee Pomeroy was to celebrate his 52nd birthday.

'At 1.01pm on Friday January 4, Mr Pomeroy and his 14-year-old son boarded a train at London Road Station in Guildford, in Surrey, bound for London Waterloo. Lee Pomeroy did not leave that train alive.'

Mr Hallam said both Pencille and the Pomeroys boarded the train within seconds of each other, albeit through different doors.

Moments later, an argument broke out between the two men, apparently over whether Mr Pomeroy was blocking the aisle.

The prosecutor said: 'As he made his way down the carriage it may be that one or both the Pomeroys were blocking his way, because Mr Pencille chose to say something to them, and the something that he said was perhaps a bit snide, because he said to them 'Ignorance is bliss'.

'And he didn't just say it once. It appears he said it twice.

'That prompted Lee Pomeroy to respond, to ask what it was that he meant by those words, repeated on the face of it twice.

'An argument began between them, and it was an argument that became heated, and it became heated pretty quickly.'

Mr Pomeroy was taking his son (pictured with him when he was younger) to London on the day he was attacked and was heard saying: 'You shouldn't have humiliated me in front of my kid'

Both Pencille and his girlfriend, Chelsea Mitchell, are on trial at London's Old Bailey

Witnesses gave different accounts of snatches of the row they had overheard.

Two passengers sitting together reported hearing Pencille calling Mr Pomeroy a 'c**t' and a 'pu**y', with one saying he 'was the aggressor'.

Pencille is also said to have threatened: 'You touch me, you touch me and see what happens at the next stop.'

The court heard Mr Pomeroy demanded an apology, replying: 'You shouldn't have humiliated me in front of my kid.'

Both men were shouting at each other and Pencille became 'very angry, very quickly', jurors were told.

During the row, Pencille phoned someone as an indirect way of making threats, the court heard, but Mr Pomeroy thought he was bluffing.

Chelsea Mitchell, who is on bail, is accused of assisting an offender. She is pictured, right, arriving at court today

Prosecutor Mr Hallam explained: 'The words she heard him say into the phone were "I'm going to kill this man" and "He'll be dead".

'Mr Pomeroy reacted to that and she recalls him saying "you got through to them quick", and so it appears, doesn't it, that by those words that Lee Pomeroy did not think Mr Pencille had actually spoken to anyone.

'But he had. Because analysis of his call data showed that he had spoken at the time to someone. And that someone was the second defendant, his girlfriend.

'A little after 1pm, and moments before he struck the first blow into Mr Pomeroy the first defendant told the second defendant that he was going to kill someone.'

Mitchell is pictured outside the Old Bailey

Another passenger recorded a section of the argument on her phone.

Mr Hallam read a transcript of the recording, telling jurors Pencille said: 'C**t, you heard what I said; you f**king heard what I said.

'Go put your hand on me,' Pencille continued before adding: 'I dare you, I dare you. Put your hand on me, because it won't end nicely.'

The prosecutor said: 'As we know, within seconds of that Lee Pomeroy had received the first wound with the knife this defendant wielded; a blow to the neck which was within minutes of its infliction to end his life.'

The prosecutor added: 'Within five minutes of boarding [the train], Lee Pomeroy had been stabbed in the neck by the first defendant Darren Pencille.

'That wound to the neck was the first of 18 injuries with a knife that Mr Pencille inflicted on Lee Pomeroy on that train on that day.

'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.'

Jurors were taken through a series of still images taken from CCTV of the confrontation aboard the carriage.

'As Mr Pomeroy remonstrates with Mr Pencille - remonstrated, not slapped, not punched, because we can see he didn't do any of those things - Mr Pencille, holding that knife in his right hand, swung it and plunged it into the left side of Mr Pomeroy's neck,' the prosecutor said, adding that it cut through both his jugular vein and carotid artery.

'The eyewitnesses, people on the carriage, saw what they thought were the two men exchanging punches.

'They didn't see the knife in Mr Pencille's hand, so they were half right.

The scene at Horsley station in Surrey, where Mr Pomeroy died after the knife attack

He continued: 'What they saw was Lee Pomeroy punching the first defendant, trying to defend himself after he had been stabbed in the neck.

'But Mr Pencille was not punching back, he was stabbing, and he was stabbing Lee Pomeroy again and again and again and again.

'The 18 wounds found to Mr Pomeroy's body when it was examined in the post-mortem examination a few days later provided dreadful proof of the savagery of Mr Pencille's attack on him.

'It was an unrelenting assault that caused Lee Pomeroy that wound to his neck, eight wounds to his torso and other wounds to his arm, his hands and his thigh.

'All of those wounds were inflicted on him within seconds of that first blow while Lee Pomeroy tried to defend himself.'

As medics rushed to treat his victim, Pencille is said to have fled with the help of his girlfriend Chelsea Mitchell, 28, who allegedly ferried him away from the scene, sheltered him at her home and bought hair clippers and razors to help him change his appearance.

The pair are also said to have searched for CCTV of the alleged murder.

Police at Hosley train station near Guildford during the investigation into the attack

The prosecutor said: 'As the emergency services rushed to save Mr Pomeroy's life, so the first defendant rushed away from the scene of his crime.

'To help him do that, he telephoned his girlfriend, the second defendant Chelsea Mitchell.'

Jurors heard she collected him, driving first to her flat in Farnham before heading down to the south coast, eventually returning later that same evening.

'In the course of that day Mr Pencille cleaned himself up and changed his appearance,' Mr Hallam added.

'The two of them, the Crown say, also engaged in research on the internet about what it was that Mr Pencille had done to Mr Pomeroy.'

The jury were told that Pencille got off at the next stop and phoned his girlfriend Mitchell, who drove to collect him.

They drove to a Tesco Extra in nearby Chichester, where Mitchell is thought to have gone inside, while Pencille hid outside.

Pencille was driven to this Tesco, where his girlfriend bought hair clippers, the court heard

The prosecutor said Michell sent him a photo of a hair clipper, which she bought, along with a razor set and some food.

They then went to Bognor Regis, where Pencille called his mother and an ex-partner. He told his mother: 'Something's happened, I've done something wrong,' the court heard.

Police tracked them down the following morning and both were arrested.

Mitchell later provided a prepared statement acknowledging she had collected Pencille, bought things for him, gone to Bognor Regis with him and been there when he shaved off his beard using the clippers and razor she purchased.

But she insisted she had no idea that he had been involved in the incident on the train and claimed any searches on her phone related to it were not done by her.

Mr Hallam explained that there was no dispute Pencille was the person who stabbed Mr Pomeroy, nor that he intended at least really serious harm when he did so.

'How could there be? He's caught doing it,' the prosecutor added. 'Mr Pencille's case is that he caused the wounds to Lee Pomeroy, those 18 injuries that I have told you about, because he was acting in lawful self-defence.'

Jurors were told a person does so firstly if they believe it is necessary to use force to defend themselves, and secondly the force they use is reasonable.

Pencille, of no fixed address, denies murder while Mitchell, from Farnham in Surrey, denies assisting an offender.

The Old Bailey trial continues.