I've attended very few of these over the years as I have been freelance for much of the last 30 years. My fisrt Christmas Party was with JWT the London Advertising Agency - in the Dorchester. There's been nothing bigger than that since. These days its booking out the pub.
Still, this one is on 12th December. I've declined being an official observer during the count for Lewes District at the Lewes Leisure Centre, and have the 13th off too. So I can drink and dance, take the train home, oggle at the results all night as the come in and recover the following day.
Or, given the way it is going, sulk for the rest of 2019 and plan how my wife and I can move back to France where the children already live and work.