Duncan Penny, prosecuting, told the trial Charles had been trying to get free beer at the bar at the promotional event organised by BlackBerry, the company Mr Sherriff worked for.
CCTV showed Charles grabbing the bottle and plunging it into Mr Sherriff's neck.
It happened very, very quickly indeed - perhaps one second, one second to take a life.
Mr Sherriff began to bleed profusely as vital blood vessels had been cut.
Mr Penny said the clash came about just after midnight after Jessie J and other performers had left.
As people tried to help Mr Sherriff, Charles was detained by security staff.
More top news
Puppies and dogs have been rescued from an address in Dagenham, after being found in appalling conditions.
Dramatic CCTV footage has captured the moment a bus driver tackled a passenger to the ground in a street fight 'over the bus fare'.
Police are trying to track down a man who sexually assaulted a schoolgirl in Bethnal Green, after posing as a plumber to get into her flat