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
A 42 year-old man from Thornton Heath has been jailed for ten years after carrying out a series of attacks on women in the City of London.
A new mansion on The Bishops Avenue in Hampstead has been bought for £33.7m.
London's mayor has launched a campaign to inform Londoners about tips to cope with air pollution.