The council offer something good, and all they get is abuse
Unlike virtually (I did notice one or two) everyone commenting here I actually live around Watford and while Watford council are usually b*stards when they do offer something good (the ability to drop your kids off for an hour or two and let they run around doing fun things with adult supervision) they get a kicking from the uninformed.
The two sites are supervised (and FREE), but if you don't trust them then head over to Cassibury Park which has a newly refurbished playground with lots of fun kit (never had those in my day, wish I was young again etc etc) and you can supervise your kids to your hearts content.
I can understand them banning parents from the site - I bet its a pain in the arse having a few neurotic parents following their kids around getting in the way.
I follow my son around the playground at the moment but that's because he's 17 months old, has no sense of danger and likes climbing! When he's five he can run about by himself and learn his own lessons about falling down. Break out the savlon and elastopasts!