I'm going here with my family next Saturday http://www.hrp.org.uk/TowerOfLondon/ Sunday opening is: 10:00 - 16:30 Also, as Peter said, http://www.sciencemuseum.org.uk/ 10.00 to 18.00 and nearby this is also http://www.nhm.ac.uk/ 10:00 - 17:50 Cheers Chris