Tens of thousands of revellers awaited the debut Glastonbury performance by the Rolling Stones Saturday, set to draw the biggest-ever audience for an event at the legendary British festival. Fans claimed their spots up to twelve hours ahead of the veteran rockers\' headline show on the Pyramid Stage, their first at Worthy Farm in five decades of performing. British broadcasters reported that third in line to the throne Prince Harry, 28, was spotted at the festival site in Somerset, southwest England, ahead of the gig. He was among some 135,000 festivalgoers gathered on the sprawling 900-acre farm for the country\'s most popular celebration of music and performing arts. Stones frontman Mick Jagger flew in by helicopter on Friday with his girlfriend, designer L\'Wren Scott, as hundreds of people mimicked his trademark dance moves in a \"Jumping Jack flashmob\". Jagger himself -- who turns 70 in July -- proudly tweeted a photo of the luxury yurt where he was to stay, while guitarist Ronnie Wood on Saturday tweeted a picture of himself sporting red gumboots. \"Heading to #glastonbury -- despite the heatwave my red wellies are ON!\" he wrote. The rockers behind \"Angie\", \"Sympathy with the Devil\" and \"Satisfaction\" have been playing a series of North American dates on their \"50 and Counting\" tour ahead of several British concerts this summer. It is the first time they have agreed to play at the Glastonbury festival, which started as a hippie gathering of 1,500 people in 1970, eight years after the Stones were formed. Glastonbury now has 58 stages and formal accommodation ranging from pre-assembled tents to glamorous yurts costing several thousand pounds. But there is still something special about the festival, which continues to sell out months in advance despite the almost inevitable mud. Stones guitarist Keith Richards said he was \"looking forward to it because it is an iconic gig and it\'s an iconic band and finally the two meet at last\". He told BBC radio: \"In a way it\'s kind of weird that at last we\'ve made it to Glastonbury. It\'s like building Stonehenge, right?\" The band are due on stage at 9.30 pm (2030 GMT), with the set list a carefully guarded secret. The Stones are expected to play for more than two hours, in a performance likely to involve pyrotechnics and special guests -- as well as a mechanical phoenix which has been set up on top of the stage. Among the crowds, Formula One design engineer Chris Kneller, 25, from Kent in southeast England, said: \"It\'s going to be one of those classic Glastonbury moments... I can\'t imagine how crowded it will get.\" Victoria Hamilton, also 25, from Wales, wearing a T-shirt showing the Stones in the 1960s, said: \"I don\'t know how they do it at their age. \"I\'d love it if Adele came on with them,\" she added, referring to the popular British singer.