We didn't actually go inside anything other than the National Gallery or the British Museum - merely the outsides of buildings. Most of them would have involved too much expense or prior organization to go inside. The problem of speed tourism would be rather different if we were trying to fit in the interiors too!

I had to look up the Pisanello piece, but yes! It's a lovely painting!

We were - but it was worth it.

It's even easier to be a tour guide if the guidee has more than 2.5 hours available for it! I rather like tour guiding - my knowledge of many of the sites is limited, but it's an excellent excuse for me to get to be a tourist now and again.

We didn't actually go inside Westminster Abbey. At 10 pounds, it didn't seem worth it just for five minutes, which is all we could have allocated for it. (It really is lovely inside though, though rather cluttered. Of course, the clutter is part of why it's worth seeing, given what kind of clutter it is.)

Given more time, I'd actually go inside Westminster Abbey and see more than one piece in the National Gallery. Going inside the Tower of London is a good choice too - also, that'll give a chance to see Tower Bridge, which we couldn't really with the bulk of the Tower in the way.

If I had more time still, my next vote is for a walk along the South Bank, especially the bit between Southwark Cathedral and the Tate Modern, taking in the Globe along the way, and possibly ending up at St. Paul's. It gets in a bit more of the modern side of London along with a sense for how rich the terrain is with older buildings and remains (i.e. Winchester Palace).

Many people go on the Eye when they visit these days (I extrapolate from my own visitors), but that's only good if it's a clear day. Actually, the Eye is better for people who already know the city, I believe, as it's a more meaningful experience.

I've never seen it there. It's in the Sainsbury Wing of the National Gallery.

I like the Buck House/St. James Park loop as an easy way of incorporating a sense of how much park and green there is centrally located in London. Regent's Street has better architecture, but there's enough of an ambient sample along the route anyways to give a sense of the city's diversity, if not necessary particularly fine examples of all of it.