Would 20 pounds on the Oyster Card suffice for 4 days of travel on tube's and buses? Plan on Tower of London, Buckingham Palace area, Covent Gardens area(RS walk) also a Victoria and Albert Museum, Albert Hall, a few Museums,few evenings dinner out in different areas. Some idea would be appreciated.
34 pounds would probably be more realistic. 8.40 is the peak daily price cap x 4 days.
It is definitely a good amount to start with. Keep in mind that you can check your balance and "top up" your card easily at a ticket machine in any station. All you do is touch your card to the reader and it tells you your remaining balance. You can then choose to add money (e.g. another 5 or 10 GBP) if you are getting low. I take the tube a lot and find I usually hit the daily offpeak max for zone 1-2 so I tend to average around 7 GBP a day.