If I had only three days, I'd spend it all in London and walk, and walk, and walk. I suppose if it were raining, I'd think otherwise. I ran Micca ragged when I was visiting. He had to stay home and recuperate after the first day we spent together in London.
Heck you could spend a whole day just exploring the marvelous railway stations in London, and another day just getting a taste of museums, and another day in Greenwich.
I was disappointed that they were charging ten pounds to visit Westminster Abbey, and another ten pounds for St. Paul's. All I wanted was to step in and take a peek. The National Gallery and the British Museum had free admission.

-Joe-