Affluent banks in Madrid bagging working capital (8)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

RICH for affluent, M[adri]D has  ON = working inserted (bagged). Richmond is a town in Yorkshire, and Richmond-on-Thames is a London borough. There are also some Richmonds in USA, one of which is the capital city of the state of Virginia, so it is a capital of sorts. I’d have thought ‘capital’ usually refers to a nation capital but that’s not so here.