Last time I was there, for some work reason I literally just remembered, I was told that you can use a credit card on (I think) all bus and tube journeys as if it's a travel pass, up to a certain maximum fare after which you're no longer charged. Something like that, though you'd best check for details.
At the age of five, Skagra decided emphatically that God did not exist. This revelation tends to make most people in the universe who have it react in one of two ways - with relief or with despair. Only Skagra responded to it by thinking, 'Wait a second. That means there's a situation vacant.'