By Mike Collett-White
LONDON (Reuters) - The Glastonbury festival opened its gates on Wednesday to 150,000 fans ignoring forecasts for rain and muddy fields to hear U2 and Beyonce alongside a bewildering choice of smaller acts from Spliff Richard to punk poet Attila the Stockbroker.
Now in its fifth decade, the event has grown from a humble gathering of 1,500 people on Michael Eavis's Worthy dairy farm in 1970, each paying one pound ($1.60) and receiving free milk, to a giant five-day celebration of music costing 195 pounds for a basic ticket.
The main talking point in the build-up to the festival, held most years on a sprawling site set in picturesque southwest England, is the weather, and the outlook this year looks more mixed than the sun-baked 2010 edition.
Heavy rain means shin-deep mud, leaking tents and sodden crowds, but Britain's Met Office is predicting sunshine, clouds and light rain at the event which ends on Sunday night, and punters are advised to pack sun cream as well as raincoats.
The biggest shows kick off on Friday, when the main Pyramid stage will host blues guitar legend B.B. King and contrarian Manchester singer Morrissey in the lead up to Irish rockers U2, the opening headline act.
The band had been scheduled to perform in 2010, but were forced to cancel when lead singer Bono injured his back.
Drummer Larry Mullen, Jr. said the set, before a crowd of some 100,000 standing on a grass slope leading down to the stage, posed a new challenge for the group, which has honed its live act on a record-breaking world tour that is still ongoing.
"It's not the 360 Degree show, we're out of our comfort zone and that's important for us," he told BBC Radio.
"Despite everything we have something to prove and it's about the songs. It's about a band being able to get up and play the music and there aren't bells and whistles necessarily. That's a challenge for us and we've got something to prove."
Coldplay, who fill the headline slot on Saturday night and release a new album soon, confessed to some nerves, despite, like U2, being one of the biggest bands on the planet.
Glastonbury is part of an increasingly crowded live music calendar in Britain, but remains the "mighty mother of all festivals" in the words of music website Pitchfork.
"It's one of the few shows that we'll get really nervous about," said Coldplay drummer Will Champion. "When we're doing our own stuff there's a very set routine ... At a festival it's different," he told BBC, the festival's official media partner.
According Eavis's daughter and Glastonbury co-organizer Emily, Coldplay lead singer Chris Martin helped the festival secure Beyonce Knowles for the final headline slot on Sunday, which brings the curtain down on the event.
Knowles' husband Jay-Z performed at the event in 2008, a choice which upset some members of the British rock establishment like Oasis, who argued that Glastonbury was not the place for U.S. hip-hop.
The rapper answered his doubters with a rousing set, and the choice of Beyonce this year barely raised an eyebrow.
Pop pundits have singled out performers including Tinie Tempah, Plan B, Paul Simon, Primal Scream, Mumford & Sons, The Chemical Brothers, White Lies, Queens of the Stone Age, Cee Lo Green and Ke$ha as ones to watch across dozens of stages.
Michael Eavis recently lamented the decline of political activism at Glastonbury, which he conceded was an event not everyone could afford, and those who could came chiefly "to have a good time.
"It gives Glastonbury soul and gives it back its purpose," he said.
"I place these values very highly, and recently I've been lamenting a bit of a decline. Tickets are good value, but not everyone can afford them. I hate to admit it, but the political platform has been reducing."
Some of that spirit may be restored if Art Uncut, a small pressure group lobbying for funding for arts and public services in Britain, manage to drum up support for their "Bono Pay Up!" protest at this year's festival.
The group plans to demonstrate against U2's decision several years ago to move part of its operations to the Netherlands from Ireland for tax purposes, a move that split opinion among fans.
(Reporting by Mike Collett-White, editing by Paul Casciato)