The oldest Tudor palace in England with many attractions including the Tudor kitchens, tennis courts, State and King's Apartments, and a wonderful maze to delight the kids.
Woodstock, Oxfordshire Train: Oxford (0)1993 811091
Not really London, but in fact, Oxford, one hour from London by train. Blenheim Palace, home to the 11th Duke of Marlborough, is nothing short of a huge, fantastic pad that we all wish we lived in.