In the best traditions of any British outdoor event, it of course poured down with rain, then cleared up with sunshine, before pouring down with rain again. No one seemed that bothered. The children seemed to relish the weather.
Check out the remarkable history of Abbey Gardens "a community garden in West Ham surrounding part of the ruins of a 12th century abbey" and the "Plaistow Landgrabbers" here, here and photo here.
(double click photo to bring up details)