London Oyster Card

The website www.toptiplondon.com has a pretty clear explanation of the Oyster cards, including a table showing the daily cap, which I never really understood before.

National Rail has some very good 2-for-1 offers, including the Tower of London. To get them you will need to buy one-day, zone 1-2 paper travelcards with the National Rail logo on them from any National Rail station (not Tube stations) for each day you plan to take advantage of an offer. To see the list of offers and to print vouchers for the ones that interest you, go here. If you don't plan to go to any of the places on the list and if you will arrive at Heathrow, then just buy two Oyster cards there and load them with some pay-as-you-go pounds. For a comparison of the advantages of Oyster cards and travelcards, go here.

I ordered before (from raileurope.com) just so when I arrived I had one less thing to do. I got it loaded with 20 pounds and figure I can add more later if I need. I'm sure others will disagree, but I like to do as much as I can beforehand so I can land, stop at the atm and enjoy.

Diane, That's difficult to answer without having some idea on how often you plan to travel on the Tube? If you plan on using it frequently, the Oyster card is very convenient! I purchased my Oyster card at London Victoria when arriving, rather than buying online. It only took a few minutes, so it wasn't a huge inconvenience. One point to clarify - you mentioned purchasing an Oyster card (singular). You will both require a card. You might check your local Library, as the Guidebooks have a good description of the pros & cons of the various London transportation options. Happy travels!