What was going on in St James's square tonight?

[Twanger]

Pushed through just before 7 and it was full of cyclists. Couldn't stop, as I was in a hurry, but it looked intriguing.....

(That's the SJ square in London...just north of Pall Mall)

 

[Molecule Man]

This I guess:
http://londonist.com/2009/06/cyclists_picnic_tonight.php

 

[Twanger]

Oh.