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
Labour’s Marshsa de Cordova hopes her experience will lead to more people disabilities being elected as MPs.
Passengers were evacuated from Tower Hill at lunchtime as flames appeared inside one of the carriages.
A parent who drove at a teacher because he wouldn't allow access to the school car park, carrying him on his bonnet, has been jailed.