What to see in London in a few hours?

Took in your suggestions. Stopped at Beaufort Hotel by Hyde Park. Shopped in Harrods - ouch! Saw the Palace - lovely. Browsed the British museum. Used the tube/underground. Rode a London bus. Cab drivers are friendly. Thames lunch cruise very cheap. Pre flight check-in not really what you think. Off soon to warmer climes. Thank you all.