For London architecture and the way it has blossomed in the last 30 years, you could also do a lot worse than getting on a DLR Lewisham train at Bank and sitting upfront. You get a great view of some fascinating modern architecture as you travel through Docklands.

Then get off the train at Cutty Sark and explore Greenwich Market and Greenwich Park. I love Greenwich, so I'll be a contrary view to others. I think the Royal Observatory is well worth a visit. (You can see enough of the Cutty Sark from the outside for free, no need to go in.)

That said, I'm biased -- we took our wedding photos in Greenwich Park and at the Cutty Sark!

Another off-the-beaten-path place that is worth a brief visit: Hoxton Street Monster Supplies. Everything the good vampire/goblin needs.

If you go to Hampton Court Palace you must try the maze; but across the street from the side entrance, there is another big Royal Park called Bushy Park. That's my home turf and it's beautiful. If you go past the Diana Fountain (no, not that Diana) and off to the left, you'll get to the Woodland Gardens, which are exquisite. And watch out for the deer!