"A really, really big school fete." "An urban, mud-lite mini-Glastonbury." It's always tempting to summarise an event by comparing it to something else, but the Camden Green Fair is unique in having a familiar, low-key village atmosphere in an unusually large urban setting. In its 20th year, I'm sorry to say that it's the first that I've heard of it, but that it has reached a wider audience must have something to do with spreading the message via social networks. The aim is to inform visitors and Londoners about the wide range of sustainable and ethical products and services - in an especially mellow and family-friendly environment. This, it certainly achieves.

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I approached from the south and headed roughly to where I thought it should be (and where the music was coming from) - though there were a few people aimlessly drifting in the Marylebone Road corner. The main park road south of the venue had been closed to traffic and was an ant-hill of activity. 'Bike Fest' had a range of activities and advice for those thinking of taking the plunge and cycling across the capital, plus a free mechanical overhaul for your bike.

The entrance in the south-west corner had a miniature festival feel with live music, (of the eclectic, dub variety), powered by humans on bicycles running a green, mini-generator. When I first arrived, they were polling for 'hamsters' to run the bikes, but by the time I left there was a sizeable and deep queue of listeners, prepared to pedal for the cause.

The central area was the kids activity centre and brought back memories of school sports day. This was the venue for the relay races, welly-'wanging' and general silliness. You'd have to possess a heart of stone, to not crack a smile here. The surreptitious cheating by the very young, the sheer hopelessness of some parents: a few adult competitors in the welly-wang, managed to let go far too early and lofted the boot, all of 3-4 inches - delighting the junior crowd. MC'd and controlled by a very able bunch of 'failed athletes', who managed the give the large event a 'small feel', and that's a good thing. Sometimes, London can be 'too cool for school'. Occasionally - [publicly] humiliating yourself can be an excellent tonic for the dreaded smugness that accompanies middle-age.

Nearby, there was modest sound stage where a group of Celtic musicians, beat a steady and relaxing rhythm which prompted a young girl (with animal face-paint) to get up and dance some traditional steps - heartwarming. Surrounding this central area were numerous stalls promoting everything from “turn off the ‘leccy more”, to ethical fashions and building sculptures from waste products.

I also managed to catch some Brazilian Capoeira, as I sat down to enjoy a snack. There's nothing more relaxing than watching people somersault and energetically sail through the air as you lay back and feed. The range of food and drink was especially strong, with a popular Jamaican BBQ stall, Moroccan tagines and an abundance of vegetarian falafel. Plenty of bar tents were serving traditional beers and ciders, so queues were kept to a minimum.

As I wandered off it was refreshing to consider the range and diversity of the attendees who had come together to try to preserve something important to all - but so easy to overlook in the all-encompassing detail of a 'busy' life. And the sun even put in a brief appearance - ah, heaven.