In pictures: Huge crowds stretch for more than 2 milespublished at 15:56 Greenwich Mean Time 11 November 2023
These pictures taken from above give you an idea of just how many people are protesting today.
At the moment, the march is extending from the Hilton Hotel on Park Lane to the US Embassy in Nine Elms - a distance of roughly 2.5 miles.
Police have said about 300,000 people have attended today's march.