REVOLVER:THERE'S A GREAT story in Johnny Rogan's biography of Van Morrison about a party attended by the well-known republican figure Bernadette Devlin. The book recounts an incident when someone at the party put on a copy of the just-released Astral Weeksalbum which led to Devlin getting up to leave for another room where "she remained for the night – singing sad rebel songs with her Northern friends and looking disapproving".

There have been similar disapproving looks aimed at this year’s Glastonbury Festival, which starts today, from musical/political ideologues who have been shouting “Sell Out” for the past 41 years.

From first charging an admission fee to erecting a security fence around the site for safety reasons to booking a hip-hop artist as a headliner, there is always a sanctimonious cabal harking back to the “old ways”.

This year the Musically Correct have been looking disapprovingly at the main stage headliners – U2, Coldplay and Beyoncé. In all the indie hand-wringing about Glastonbury – “so bourgeois, so mainstream” – the central point seems to get lost that Michael Eavis runs the festival as a non-profit event. He demands (and gets) the big-name acts to go out for 10 per cent of what they’re usually paid on the commercial festival circuit and all profits go directly to WaterAid and Oxfam. The bigger the headline name, the more people come and the more money is made for the charities.

Eavis doesn’t even allow telecoms or alcohol companies to advertise their wares and short of turning the whole shebang into a Crusty Free For All with The Levellers and Chumbawamba there’s not much more he can do – what with the minor detail of having 150,000 people to entertain for 72 hours.

Glastonbury can and does wreck your head with its roving armies of eco-Nazis who glare at you if you so much as get confused by the colour-coding of the eco-bins. And you may never want to see or hear the word “holistic” ever again after a weekend at the festival.

Glastonbury may have become an institution, but, contrary as ever, Eavis has decided that “people are having too much of a good time” at the expense of the core festival message. He’s disappointed by the apathy shown by this generation to swingeing cuts while financial institutions are, at best, slapped on the wrist.

“I want the festival to become more of a sounding board of political discontent,” says Eavis. “Politics gives Glastonbury soul and gives it back its purpose. I hate to admit it, but the political platform has been reducing. If people are really faced with dire circumstances, that will get them angry and motivated, and that’s the way we’re heading at the moment.”

This year Glastonbury will be welcoming groupings such as 38 Degrees, Climate Camp, UK Uncut and False Economy in the hope that they can rejuvenate the old festival regulars – such as the greying anti-nuclear crowd and the knit-your-own-organic-tofu-sandals end of the Green movement.

It’s always a delicate balance between the pouting supermodels and their entourages locked into their own VVIP prison backstage (though this year Eavis has banned Kate Moss from having her usual celeb-only party) and the more militant types up in the Green Fields who spend the weekend in an alternative prison of ideological dialectics. There are those who couldn’t possibly be seen anywhere near something as commercially vulgar as the main stages and retreat to a forest of musical fundamentalism, sharing space with those who are just there to get out of their head and enjoy whatever act they can keep it together long enough to enjoy.

And all this dissent and contradiction and truculence merely adds to the ineffable appeal of what is a truly magical festival. It is why, for many people, Glastonbury remains the best thing in the world.

MIXEDBAG

Watch out for some arch comments from Morrissey as he opens for U2 tonight on the Pyramid Stage. And after his sublime Vicar Street appearance on Monday, don't miss Paul Simon's set at Glasto 

Beyoncé is currently doing a medley of Bohemian Rhapsodyand Sex On Fireduring her set. Cease and desist, love – it's bloody awful.