what to do in London

Hello everybody. I m Inna. I dont live in London/ But i got a friend there. For some reason he was staying at home for several years almost without going out. Could somebody recommend me some hobby for him. He needs just to socialise, to go out. Some activity that will involve him all..He s got some problems with health, so no sport, no walking for long. Anyway-recommend me everything that i can advice him please. Thank u so much.