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
Police are attempting to find a vulnerable missing 16-year-old girl who is feared to be with a 51-year-old man.
The owners of two Hackney bakeries have had to pay £28,000 after infestations of cockroaches and mice were found on the premises.
After failing to get his hands on any tickets for Arsenal fans for the FA Cup final, one unlucky supporter appealed for Royal assistance.