I don't know what plans Horniman have for crowd management but I think it is fairly clear to spot the difference in the park between 5, 10, 15, or 20,000 people. Even without tickets being issued it is relatively simple to estimate numbers with a 20% margin of error. It is also relatively simple to prevent greater numbers entering the site by closing the gates.

What is at least as important as exact numbers inside the park on their busiest days is the impact outside the park. Assuming people still want occasional events with 5-10,000 people in the park, what needs to be ensured is that people coming from outside Forest Hill are encouraged to come by public transport, that there is better sign-posting for local car parks, and that inside the park there are adequate toilet facilities for the numbers in attendance (as there usually are).

There have been many large events in Horniman Gardens over the years, which have been great for the local community and bringing some additional people to Forest Hill. There have been one or two that were too big and the Horniman do not wish to repeat events of this size. But I enjoy the occasional large event in the local park and so do thousands of others. Long may they continue!