In London for the afternoon tomorrow with DD11 and niece 21. Arriving about 1pm, and leaving early evening for hotel elsewhere. We don't know London well, but did tick off Tower of London, boat trip, London Eye and sightseeing bus earlier this year. I've looked at Buckingham Palace (DD super keen, niece isn't) and both would like to go to the big Lego shop. Any advice on something to do for a few hours that feels exciting and 'London-y'?