An art director accused of killing a BlackBerry manager at a Jessie J gig told a court he feared the victim was going to beat him up.
Ashley Charles, 26, said Phillip Sherriff, 37, had become aggressive and abusive as the pair jostled for space at the concert’s free bar.
Dad Mr Sherriff barged against him before phoning a friend and loudly discussing how they were going to ‘do’ him, the Old Bailey heard.
Terrified Charles claimed he had then tried to stop the situation from escalating by grabbing a bottle of Becks from the victim’s hand.
But he ‘instinctively flapped out’ and ended up using the bottle to slash Mr Sherriff’s face, he told jurors.
The blow severed the father-of-two’s carotid artery and jugular vein causing massive blood loss and he died in hospital four days later.
Mr Sherriff had travelled from his home in Scorton, near Garstang, to attend the event at the Pulse nightclub on central London’s South Bank last April 3.
Charles was at the party with his brother, who had won free tickets in a competition organised by BlackBerry.
He told jurors he had been heading for the bar alone when an unknown woman approached him and started making small talk.
As the crush for drinks intensified, he said he had asked Mr Sherriff: ‘Excuse me, fella.
‘Do you mind giving me a bit of room, please?’
But he claimed the victim ignored his request and replied: “She doesn’t want to be talking to you.
“She’d much rather be talking to me, wouldn’t you, love?”
After ignoring the comment and turning his back, Charles said he had then felt a ‘shoulder barge and a grunt’.
“I stopped and tried to assess what was happening,” he told the court. “It was Mr Sherriff.
“I said, “What’s going on?” but he’d begun to use the telephone.”
He told the court he heard Mr Sherriff say that he was going to “do” him.
Charles said he was ‘fearful of trouble being arranged’ and made a vain attempt to snatch Mr Sherriff’s phone from him.
“But he smiled at me and basically told me I was in trouble,’”he added.
“I took the bottle off him. I instinctively flapped out and slapped him.”
He insisted he had not broken the bottle beforehand and suggested it must have struck something else before it connected with Mr Sherriff.
Asked if he had intended to injure Mr Sherriff, he replied: “Absolutely not. I was unhappy. I was devastated.
“I didn’t intend to harm him and I could see he was hurt.”
Charles, who has no previous convictions and had never been arrested before, said he had owned up, but denied claims by police he had boasted of ‘bottling’ Mr Sherriff.
Charles, of Nevanthon Road, Leicester, denies murder.