Mentioned by London 2 days itinerary
2 Days in London: The Perfect London Itinerary
"You could also really go museum crazy, and drop in at either the Natural History Museum or Science Museum, both of which are free. If you’re into pageantry, just round the corner from Buckingham Palace, and officially part of the grounds, the Royal Mews is a fascinating place to visit, and much less popular than its exhibits deserve. Finally, if you’re into afternoon tea, you can experience a fashionable take on the high tea experience at the Berkeley."