It was the Bath Half Marathon today. This blip was taken on the first (and only I think?) hill of the course, looking back on the runners as they came up from Green Park to Queen Square. I think it nicely captures the scale of the event, though actually this was just the first of runners going thu - the main group went on and on for ages.
I take my hat off to everyone who took part. It's a fantastic thing to watch.
I've put a selection of other images on Flickr if you are interested.