We use "Tailgate" but no we turn up in all sort, motorhomes, trailer tents, tents, some of the folk's book hotels nearby. As you see from the writeups we all cook whatever we want to, aim for 5 pm or so, all the dishes are laid out, and everyone helps themselves, we then sit & relax chewing the fat and partaking of the falling down water.
With you being in London, the first one of the year is usually the East Anglia tailgate...then we have the Midland one, followed by the National then the northeast one.
Ice.