Travelling on his own magical mystery tour, Brian O'Connellheads to Europe's biggest music festival in the back of a van

To most people the text would have been like a golden ticket moment: "Hey, we have room in the van for Glastonbury: wanna tag along?" The author was traditional singer Pauline Scanlon. I'd become friendly with her and guitarist Donogh Hennessy a year earlier when I wrote a feature about the duo for this paper.

Did I want to tag along? In truth, no. You see, three years ago I spat out the hooch, spurned the sauce and let go of the world of liquid libation. I'm talking about sobriety folks, a real hush-hush subject, where weekends revolve around household cleaning, morning strolls, and nightly raids on your local video store. So the idea of three days on a Somerset farm with 170,000 revellers, in various stages of inebriation, was more than horrifying - it was somewhat sadistic. Yet it's amazing how persuasive backstage passes can be. I might be sober, but thankfully I still have my senses.

Friday afternoon, 13.18 pm, and Hennessy and Scanlon are scheduled to appear in the acoustic tent in a little over two hours' time. Routine nerves are heightened by news earlier that morning that their double-bass player, Martin Brunsdale, cut his hand while gardening and won't make it. The pair are on their own, set lists need to be altered and song structures re-thought. It's not ideal preparation for Scanlon's first solo show at the world's largest greenfield music and performing arts festival in the world.

Driving down narrow lanes and through opened gates, the sheer scale of the festival begins to hit home. By Thursday night over 100,000 attendees were already on-site, unfazed by the bleak weather forecasts. We are directed to the artists' campsite, where power showers, clean toilets, and on-site catering are provided. I'm now a bona-fide member of the band, with the artist pass dangling off my neck to prove it. Backstage, volunteers are on hand to allot dressing rooms and make sure each band's food and drink rider is provided. I sneak a look at headline act Damien Rice's requests - all fruit teas and cheese boards with dark chocolate, about as decadent as it gets. I was going to fit right in.

Hennessy changes guitar strings in the van and reflects on his last time here playing with Sharon Shannon. They were down to headline the Friday night, immediately after The Waterboys. Mike Scott was in jovial mood, telling the band beforehand he was going to "blow them away". Shannon and crew took to the stage and everyone was up for this one. Two minutes in, the PA blew, and what should have been a frenzied assault on the Glastonbury masses ended prematurely. So, in a sense, Hennessy has a score to settle. "I'm really nervous now," admits Scanlon, "we really could have done with the bass." "Let's not worry about it, we do what we do anyway," Hennessy reassures, leaving the green room and taking to the Glastonbury stage for what would be a beautifully intimate performance.

When people talk about the mud at Glastonbury they tend to downplay its significance. At certain times it's like the ground has become one huge suction pump unwilling to let your feet go. With extra festival areas added this year, getting from one end of Glastonbury to the other took upwards of two hours. In the lead up to the event over £1 million had been spent on upgrading drainage systems, in an effort to avoid the flooding which has plagued past events.

Yet by Saturday morning the site had become a moving sea of mud. The area around the acoustic tent was as good as it got, yet extra wooden tracks still had to be laid down and bands had problems getting their equipment in and out of the stage.

The Arcade Fire were the talking point of the previous night, taking to the Other stage with a performance of spectacular intensity, noticeably lacking in the other mainliners. Before them, Rufus Wainright also showed how to work a crowd, appearing for an encore in full drag while his band swapped their instruments for jazz hands. Over on the main stage, The Fratellis, Bloc Party and even headliners The Arctic Monkeys all struggled with the scale of the site, and never looked in danger of igniting the Pyramid stage.

Back at the acoustic tent, Jerry Fish and his Mudbug Club had just landed. The ex-Emotional Fish frontman has become something of a festival favourite on the back of acclaimed outings in 2004 and 2005. His big band sound, on-stage theatrics and festival bonhomie all lend themselves to the atmosphere, where the underlying ambition is to have a good time. Two songs in, and Fish, aka Ger Whelan, had left the stage and got down and dirty with his audience, performing some of his set from the middle of the near-capacity tent.

Afterwards, he reflected on the attraction of playing the festival. "Glastonbury is one of those things people have to do in a lifetime," says Whelan, "I think our act suits the festival. Glastonbury is not just about music, it's also got theatre and circus and performing arts there." Naturally, the conversation turns to mud. "I actually think it's muddier this year. We've been here three times now and it gets muddier every time," he says. "It's kind of a soupy mud this year - that's the great thing about Glastonbury, there are different classes of mud."

For many of the acts playing, financial gain is not foremost in performers' minds when tackling Glastonbury. In truth, many of the acts take a loss to play the festival, reducing their fees significantly in the spirit of charity on which the festival was founded.

"It's all about the prestige of playing probably the best-known festival in the world," says Whelan. "There's something addictive about it, and for us it's great to be back again this year." Of Saturday's main acts, Paul Weller was a surprise highlight, while Ed Byrne was punching above his weight in the Cabaret tent. Over on the main stage, The Killers never really got going, thanks largely to a dodgy PA, which had large sections of the audience chanting "turn it up" and "louder" between songs. On Sunday, it was good to see Billy Bragg still fighting the good fight on the Avalon stage and sounding better than ever, while Shirley Bassey was a clever addition to the evening bill. Overall, despite the somewhat diluted line-up, the event was deemed a huge success.

The statistics for Saturday alone speak for themselves: 165,00 punters on site, adding to the 30,000 workers and volunteers already in place. Medics had treated 1,268 people, with 32 of those taken to hospital. Some 163 offences were committed, with police making just 121 arrests. The tent-theft tally was 29, up from 14 in 2005, but still impressively low given the numbers attending. All in all, festival organiser Michael Eavis sounded optimistic about the future of the event he founded almost four decades ago. "In a way, I'm glad it rained," he said, "We needed the showers to test out our new drainage system. The ground has held up a lot better than it did in 2005, despite the fact we've had just as much rain." Suffice to say, there weren't many sightings of Eavis rolling out his groundsheet in the streams of mud that doubled as campsites, preferring instead to tour the site from the comfort of his Range Rover. Already his sights are on next year: "We have got one very special band lined up to play next year's festival. I'm looking forward to it already."

Perhaps the problem for music acts at Glastonbury is that there is just so much to compete with, from the ill-definable wackiness of Lost Vagueness, to the hippy enclave of Green Fields, and the ongoing sport of people watching. What's happening on stage has become something of an afterthought, with the uniqueness of the Glastonbury world taking centre stage now. The real performers are strumming in the back of tents, diving into mud baths, tying the knot in the Love Chapel, or choosing the right tuxedo to match their wellies. They come for the music, but, more than that, they come to be accepted.