There were about 60 for the actual die in, which is in-line with what the organisers asked for, in order to commemorate casualties at this junction. Commuters were joining in and passing on as their deadlines required. Personally I think it's pretty impressive that you could get such numbers for something at 7.30 AM Here's an account: http://www.theguardian.com/environment/bike-blog/2013/dec/20/cyclists-die-in-vauxhall-bridge-road-safety
There were about 60 for the actual die in, which is in-line with what the organisers asked for, in order to commemorate casualties at this junction. Commuters were joining in and passing on as their deadlines required. Personally I think it's pretty impressive that you could get such numbers for something at 7.30 AM Here's an account: http://www.theguardian.com/environment/bike-blog/2013/dec/20/cyclists-die-in-vauxhall-bridge-road-safety