In pictures: Glastonbury's 40 years

The Glastonbury Festival first took place in 1970, when 1,500 people paid £1 to get in (and get free milk). But the event made its name the following year, when the Pyramid Stage made its first appearance.

Some 12,000 free spirits descended on Worthy Farm in Pilton, Somerset, for the free festival in 1971, which featured performers including David Bowie, Traffic and Hawkwind.

The early years were basic affairs. The toilets were holes in the ground with scaffold poles for seats, each separated by hessian sacks. There was no alcohol for sale and all food was vegetarian.

There were no official festivals in the mid-1970s, but the event took off again by the end of that decade. By 1984, 35,000 people paid £13 per ticket. Photo: Nils Jorgensen/Rex Features

Festival attendance has grown tenfold since 1981 and the site has expanded in turn. Additions in the 1980s included the Green Fields, the theatre marquee and a Womad stage. Photo: Ian Sumner/Glastonbury40.com

A second Pyramid Stage was built in 1981 and doubled as a cow shed. By 1992, 70,000 people were there. Photo: Leon Marks/Rex Features

Michael and Jean Eavis cheer from the Pyramid Stage pit in 1992

Michael and Jean Eavis, who founded the festival on their dairy farm, cheer from the Pyramid Stage pit in 1992. Jean died in 1999 and Michael has continued to be its driving force. Photo: Brian Walker/Glastonbury40.com

Firemen inspect the wreckage of the Pyramid Stage in 1994

Disaster struck in 1994 when the Pyramid Stage burnt down 10 days before the festival. An exhibition of festival photos takes place at Millfield School, Somerset, from July. Photo: Ian Sumner/Glastonbury40.com

In 1995, Robbie Williams was on the verge of quitting Take That when he turned up to party with Liam and Noel Gallagher. He even joined Oasis on stage for some drunken dancing. Photo: Brian Rasic/Rex Features

The hippy spirit lives on, just. From its flower power origins in the 1970s and counter culture leanings in the 1980s, the festival has become entrenched in the British cultural mainstream.

Gatecrashers became a big problem in the 1990s and the numbers getting over, under or through the fence threatened the festival’s survival after 2000. A new ring of steel was erected for the next festival, in 2002.

Despite taking place at the height of summer, the event is beset by mud with remarkable regularity. For some, the swamps bring utter misery. For others, it is a chance to take part in some spontaneous extreme sports.

In 2005, freak storms left part of the campsite under water, with rivers running through others. Two months of rain fell in several hours, cutting electricity supplies to the stages and causing performances to be postponed.

Organisers spent £100,000 on improving drainage and flood relief after the 2005 event. That provided some help in the following years, with rain falling at every festival since.

The current Pyramid Stage is now a decade old. Its structure, built using 4km of steel tubing weighing over 40 tonnes, stays in place all year round. Performers have included Sir Paul McCartney, David Bowie and Jay-Z.