The AP reports it at 2000. Some twit earlier said there were 100,000 protesters in London. AP sez 10,000.
I met a British guy at work the other day. He said that conditions in London are often quite dense and crowded. In other words, when you see 100,000 protesters in the street, on any other day you'd see 80,000 people on that street anyway. Plus it's so fashionable to be antiwar and anti-Blair, and of course it's our fault for dragging them into it.