A late Friday night building placards was followed by a busy Saturday morning collecting vans, preparing speeches and briefing marshals. At 1.50 the early arrivals were dotted around King Charles Street. The media and organisers only just outnumbered by the crowd.
Then as Big Ben started to chime, scientists in lab coats started to arrive en masse. The pictures from Flickr and many many others can tell the story.
Others have written:
Please leave links to ones I’ve missed in the comments and we’ll update later.