Dalek outside St Paul's Cathedral - why?

I took this picture sometime ago; December 2007 to be more precise. I was walking to work one morning, past St Paul's Cathedral in London, when I came upon, well, a Dalek, standing alone outside the Cathedral, as you can see above; I walked calmly on, showing no fear. I don't know quite what was going on, although I think there was a film-crew around the corner, still, funny picture, especially with the bollards that look like Daleks themselves and of course the inaccessible steps of the Cathedral - Daleks can't get up steps.