I took up position on a traffic island in the centre of the Strand in London. People were only too happy to have the pictures taken.
I used a Canon EF100-400mm f/4.5-5.6L IS USM zoom lens on my Canon 40 D to try and pick out individual faces and blur the background.
The light was not too good so I set the ISO to 800 and the image in this post was shot at 115 mm, f/4.5 1/200 sec.
The march was very good natured with a very heavy police presence; but it is a very good idea to keep aware of your environment because things can change very quickly.
This video provides a feel for the atmosphere at the demonstration