We only have 20 hours in London (on a layover for one night) on Sept 22. We will be coming in around 4:30, leaving at noon the next day. What spots should we see? We will want to have a nice relaxing dinner and then do some walking around....where would you recommend?

thanks.

why don't you try to get theatre tickets? The shows are earlier than in the US so you woulnd't be up late.

Re. the show idea - it's great if you had more than a day.
Personally I would be too bleary-eyed from the flight, jetlag (and excitement from night before) to concentrate on a 2+ hour show.

I like your idea of a low-key relaxing dinner and walking around...unfortunately I can't recommend it since we're flying in to London the first time this May.

Let me know what you decide to do. We also only have a day. We're thinking of doing a Thames cruise, nice dinner, walking around Soho and Bloomsbury, but all depends on your interests.

I like the dinner idea and how about doing a "spin" on the London Eye? That will give you a bird's eye view of London. If jet lag hits and walking seems too exhausting, you could always find a double decker bus and ride from end to end.

Do the shops, have dinner, see a show, go to a bar then roll into the airport.

I second Grasshopper's idea of maybe also doing a double-decker. You get to see all the major sights without much effort and may influence which area you wish to explore further.
IF you buy the double-decker tickets online you can take advantage of a small discount (1-2 pounds).

oops, didn't think about jet lag. Probably not a good idea for a show unless it is a hoping musical.

a London walk. look on walks.com. a great way to end the night

okay- here's what I would do- first check into your hotel and freshen up- then head straight to Harrod's- they are open until 7 PM even if you are uninterested in actually shopping, it's a must-see- hit the food halls for sure.Then I'd go to a real "londony" restaurant- Rules is my favorite- it's near Covent Garden- 35 Maiden Lane- they have a great website with wonderful pictures. Have a proper British dinner and sticky toffee pudding for dessert. Afterwards I would stroll around the theatre district or nearby Trafalgar Square. In the morning I would see either St. Paul's (open 8:30 usually) or Westminster Abbey (opens 9:30)- can't get more London than that.