I just read it on MK news also and because I was curious about this club also, I posted some information from Wikipedia there!
Information Wikipedia, why I think Mark is there at the right place:
The original plans state that The Garrick Club is instituted for the general patronage of drama; for the purpose of combining the use of a Club, on economic principles,
with the advantages of a literary society; for bringing together supporters of drama; and for the formation of a theatrical library, with works on costume. It also has a significant art collection and various theatrical artefacts.
IF the information it true then I think it is an honour for Mark to be part of this club. Not because it is exclusive and only for a few rich people, but because (If I understand completely) this is a club for very intelligent people who come together and talk about books perhaps art and serious things that happens in the world!
Besides being a great and wonderful artist, we all know that Mark loves art, to read books and of course he is very intelligent! I think he is a man that fits in all worlds!
Fieneke