Now I don't know much about football (I understand it is some form of hobby where people watch millionaires cuddle, spit, and occasionally kick a ball) but I thought Arsenal was a local team, at least until 1910.
I'm told that, unlike the players and managers, fans have to stay loyal to a team (except when they move to Milton Keynes, obviously), but it seems that good South East Londoners are bound to support the local team from Woolwich. Crystal Palace weren't even in London when they were founded in 1924.

I hope my ignorance doesn't show