Tens of thousands of people braved the traditional swamp of mud to watch the first acts of the Glastonbury festival, starting with Liam Gallagher\'s band and culminating in a vintage performance from Arctic Monkeys. The former Oasis frontman and his band Beady Eye opened the weekend with an unbilled morning performance Friday on the Other Stage, declaring: \"It\'s never too early for a bit of rock and roll echo.\" Some 135,000 revellers have gathered at Worthy Farm in Somerset for Britain\'s most famous festival of music, performing arts and camping, with a touch of the new age spirituality that goes back to its 1970s origins. Despite the mud underfoot, there was little rain Friday on a day that took in Tibetan monks, pop princess Rita Ora, and a headline performance by indie rockers Arctic Monkeys which won rave reviews. An orchestral version of their classic \"Mardy Bum\" wowed the crowd, with radio DJ Jo Whiley tweeting: \"@arcticmonkeys SOOOOO good. Mardy bum unbelievably beautiful.\" The three-day festival covers more than 900 acres, and putting it on is an epic undertaking that this year involves more than 3,000 portable toilets, 11 million litres of water and 1,500 square metres of solar panels. The Rolling Stones are to headline the main stage on Saturday, in the rock and roll veterans\' first appearance at the festival. Hundreds of people heralded the Stones\' arrival on Friday with \"Jumping Jack flashmob\" in which they mimicked Mick Jagger\'s trademark dance moves, while Jagger himself proudly tweeted a photo of his yurt.