Large social gathering, esp. one held in secret to avoid the attentions of the press, police and public.
"I want to apologise," Boris Johnson tells MPs before PMQs begins, "I believed implicitly that this was a work event"
"Which wines and cheeses should I bring to Friday's work event?"
a social occasion, often in a person’s home or garden, at which people eat, drink, talk, dance and enjoy themselves
Did you attend that banging work event at BoJo's yesterday? Rishi was off his tits on Mexican Coke!
It was a fairly standard BYOB work event.