Hardeep Singh Kohli: It's the longest day – let's party like it's 1399

There I was on Hampstead Heath in the broad daylight of a June evening. I was joined by a beautiful, cleavage-dominated American woman with sensible shoes; an anaemic looking, post-goth lady with bottle-red hair and matching accessories; a man in his mid-thirties still coming to terms with dramatic premature hair loss; an impossibly skinny twentysomething man who didn't seem to be much of a Druid but realised it was the only way he was going to make friends. And then there was me: fat, brown, Glaswegian Sikh bloke with an electric pink turban. One might have been forgiven for mistaking us for the advance party of Zippo's Circus.

The intention was that I would be holding hands with a bunch of freakish strangers in order that I might do a ring-a-ring-a-roses-type dance to invoke the gods of the summer solstice, asking them to bless the earth on the longest day so that the plants and fruit might grow for the harvest festival in autumn (at least that's what I thought we were doing). All for a television documentary. The only thing that could have made the afternoon weirder would have been if I had been asked to wear a full-length Lincoln green smock-dress that was a size and a half too small.

No sooner had I thought that than I was attired in my full-length Lincoln green smock-dress. I danced and sang and held hands and sang and danced and held hands some more. Given that it was summer and I was wearing an extra layer of clothing, I found myself crumpled in a heap, leaning against a tree. There was a beautiful moment of stillness. The gayness of our abandon made me feel like a child again. There, surrounded by the verdant, wild beauty of the heath I felt connected with Nature herself. I lay on my back and stared at the sky that was preparing a slow welcome for twilight. I became acutely aware that I was sitting on a planet that spun on an axis and was orbited by a moon in a solar system that was part of a galaxy that itself was but a slither of a wider universe. I felt small, I became insignificant. I knew my place in the cosmos and the cosmos knew its space around me. It was a deeply profound moment, broken only by a shrieking child running to his mother, frightened by the apparently dead, pink turbaned man in the Lincoln green dress.

Midsummer always meant something special to me. Perhaps it was because in Glasgow we enjoyed longer days, days that stretched inexorably into the night. There was a sense of magic and adventure. Obviously as a child I had no comparative lunar data that would have informed me of the difference in sunsets on my latitude with those of southern latitudes. All I knew was that a week before our summer holidays began, the days never seemed to end. I woke to the sun, spent all day riding my bike in the sun and then slept with it still shining. On days like that everything seemed possible. I experienced then what I now know as a cynical, experience-addled adult to be a sense of exhilaration.

Drawing a line from those childhood days to that insightful moment laying down on the earth staring up into the north-west London sky made me realise a great deal. Midsummer makes me feel insignificant again; and that is a very good thing. As a species we have tried to impose our will on the planet. We have acted with astonishing arrogance on matters we have not even begun to understand. For instance, we have attempted to collate and convey time rather than devise a system that has any abeyance with Nature. We created seconds, minutes, hours and days that had little or no bearing on how the world works. (So imperfect are our attempts that we were forced to invent leap years to correct our miscalculations.)

Britons have been celebrating midsummer for nearly 800 years, but who knows what informal and groovy dance and ritual-based festivities there were before that? Since the solstice falls within a week of John the Baptist's feast day there has been much confusion and fusion between the two. The celebration of midsummer is widespread across northern Europe, linking in no doubt with the more discernible increase in the length of the day. The once solemn, prayer-like events soon gave way to dancing, partying and general debauchery, much like my evening on the heath. (There is no indication of Lincoln green dresses in the archive, however.)

There was a belief that the increased daylight would allow evil spirits to roam freely stealing people's souls or some such spiritual crime. Thus fires were lit and folk stayed up all night (it is from this festival that we derive the word bonfire, a fire built of bones).

There has always been an uneasy relationship between the celebration of the solstice and the established church. And is it any wonder? We created organised religions that attempted to explain imperfectly our existence where they could. And where they couldn't they described inexplicable events as mysteries and expected us to buy that, to have faith in the vacuum of reason or logic.

There is something very refreshing about the Wiccan way, the Druid approach. They have no expectation that they can explain everything or indeed anything. Unlike the organised religions, Wicca is all about stuff we can see; the sun and the moon, the holly and the oak. Their godheads are based on a necessary reality, an existence that once yolked humankind to the earth and earth to humankind. Their belief seems to be founded on the realisation that we are animals and locked into project planet. And while the notion of "harm none, do what ye will" might seem familiar to Bible-lovers, it comes in a refreshingly dogma-free version with our Wicca sorority and brethren. Given what we appear to be doing to the planet in terms of warming it, melting it and polluting it, it might not be a bad time to start acting on that mantra.

I think we ought to start a campaign to celebrate Midsummer in a more spectacular way. As a species we have specialised in creating tension, division and war. I am not for a moment suggesting we eschew organised religion. What I am suggesting is that we embrace our commonality. We all exist in the warmth of the sun, the light of the moon; we live by the tree and drink of the river. I suggest that we create a pantheistic precedent and have the first multi-faith celebration of the sun, of the galaxy and of the universe. I would like this event to take place in Croydon. We should, for one long day only, forget our differences and unify under the canopy of a shared sky.

We will welcome the pot-smoking hippies, the groovy Bhuddists, the depression-embracing goths, the perennially troubled Christians, the ideologically-centred Sunnis and the daughters and sons of Khalsa. Food ought to be available for vegetarians, vegans, omnivores, and chocolate for the pot-heads. We should all wear differently coloured, full-length, smock-dresses that celebrate the colours of nature (no one, not even Croydon's own Kate Moss, looks good in a smock-dress: it is a great leveller).

There should be guitars and tambourines and a bonfire. Together we should sing in praise of light, in adoration of Mother Earth, in respect of the planet. The fire will burn brightly into the night. We will awake the next morning nestled together, differences having melted into the night and our paths a little closer to each other, more in unison with the planet upon which we find ourselves.

Maybe one day, even the longest day, isn't enough to right the world's wrongs but we really do need to start pulling together. I'm fairly sure once we have all lost our inhibitions in a singing, dancing, tambourine, guitar and smock-dress-wearing extravaganza we might be a little less self-conscious in actioning global change.