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
Some of the best stories from the past week on itv.com/london. Got a story? Email us at email@example.com
Paul Clement says he's had the perfect apprenticeship. Soon it will be time to graduate.
The puppy was taken to the RSPCA’s centre in Potters Bar where an X Ray revealed her spine was severely damaged.