One of our favourites. The park is a huge secure play area at the north end of Hyde Park. If you go on a Sunday you can park for nothing in the local roads and the activities have to be seen to be believed. Its modelled on the Peter Pan story so there is a full size pirate ship, Indian camp, adventure playground and lots lots more. Food is excellent and on a warm summers day it represents just about the best of London's kids facilities.
http://www.royalparks.org.uk/parks/kens ... ground.cfm