Actually, the question seems to be quite a lot bigger now!

From reliable sources, the Horniman are to meet shortly with the police and Lewisham Licencing re the event as the traffic and health and safety implications caused a number of concerns in many circles. Apparently their alcohol and entertainment licence was for events of no more than 5000 people so clearly there has been a breach here however inadvertantly caused by the unexpected success of the cook out. However it would appear that if they are to consider hosting the event again or other events where similar numbers are expected then they will need to apply for a completely new licence for events up to 20000 people. This would enable them to hold several events of this nature if they are successful in their application. If they are to be successful in their application they will need to produce a strategy for handling the expected numbers of people and additional traffic produced for each event. The same question arises as to whether this will pose so many restrictions on any such event for it to be enjoyable and worthwhile.

I am getting some contact numbers and names and will post them as soon as I am able to in case others find this useful.