Jurors were told Phillip Sherriff had been at the bar of the Pulse nightclub in central London at an event where pop star Jessie J had been performing when there was jostling by Ashley Charles who was trying to get free beer.
After becoming irritated, Charles grabbed a bottle from Mr Sherriff’s hand and slashed it into his neck, said Duncan Penny, prosecuting.
He told the Old Bailey: “Eyewitnesses described it as a swipe or slash. It happened very, very quickly indeed – perhaps one second, one second to take a life.”
As people tried to help Mr Sherriff, Charles was detained by security staff.
After being arrested by police, he said: “Yeah, I know I bottled him. He kept pushing past me through the bar area.”
Mr Sherriff had travelled to London with colleagues for the promotion event on April 4 organised by Blackberry, the firm he worked for.
Mr Penny said the clash came about just after midnight after the performers had left.
He alleged Charles, 26, became annoyed with Mr Sherriff who was joking about. The defendant had been trying to get to the bar and squeezed between Mr Sherriff and a woman.
“He continued to jostle Mr Sherriff after he obtained two bottles of free beer,” said Mr Penny.
Words were exchanged about the woman and Charles tried to grab Mr Sherriff’s mobile phone from his hand before snatching the bottle “in a flash”.
Charles, a creative director, sat in the dock and watched CCTV footage of the attack.
Mr Sherriff’s widow Jane wept a few feet away at the back of the court.
(The trial continues.)