I have a 12 hour layover in London so I really probably have about 7 hours in the city itself by the time I get in there and need to give myself 3 hours before boarding the 2nd leg of the journey.
I'm thinking of walking around the London Brige and the Tower of London and then shooting over to Buckingham Palace, London Eye, Westminster Abbey and Big Ben.
I'll be buying a Heathrow Express pass from the airport to Paddington Station. What tube tickets will I need to purchase for these zones? Should I get a day pass or what do you recommend for these areas? I'm not familiar with how far Paddington is from these spots as well.