Is nothing sacred? The Solstice isn't what it used to be...

On the longest day of the year yesterday in Wiltshire, the sun rose above a green horizon and kissed the ancient monument of Stonehenge. But while the arc of the sky has not changed over the past five millennia, the gathering that greets the summer solstice each year has become something very different from its earliest incarnation.

The worshipping pagans of prehistory who may have circled the stones would not have had their peace disturbed by passing traffic on the A303, for a start. Secondly, though the precise purpose of the site remains a contentious issue, not even the most maverick of historians would suggest it has ever been an arena for drink-fuelled fist-fights between bare-chested men in tracksuit bottoms.

Police patrolled the site where 20,000 revellers greeted the sun's first rays yesterday morning, making 20 arrests. Eleven were for drug offences, five for breaches of public order, and 47 drug seizures were made. St John Ambulance treated 60 casualties on site for minor injuries and transported four people to hospital. A local news agency photographed young men fighting each other: one had a bloodied mouth.

The summer solstice, which usually falls on 21 June, is the only day on which the public is granted access right up to the stones themselves, without prior appointment. Many people are drawn by this unique cultural opportunity. Thousands have since followed, drawn more by the urge to have a good time.

"There was a high degree of narcotic and alcohol-induced revelry [this year]," said Philip Mould, an art expert on the BBC's Antiques Roadshow. "We saw people being hoiked away. Although overall it was a peaceful and cultural event."

Throughout the 20th century, Stonehenge began to be revived as a place of religious significance, by adherents of Neopagan and New Age beliefs, particularly the Neo-Druids. Men, women and children in their long white robes, and flowing beards, form a significant portion of the party who mingle freely with the less religious attendees.

Numbers were lower this year than previously, owing to the poor weather in the run-up to the event, and because the last few years had seen it fall on the weekend. But the rain did little to dampen its growing reinvention as another date on the summer calendar of hedonism.

When Stonehenge was first opened to the public it was possible to walk amongst and even climb on the stones, but they were roped off in 1977. Arthur Uther Pendragon, an eco-campaigner and self-declared reincarnation of King Arthur (born John Timothy Rothwell, in Yorkshire), protested against the decision and picketed the site. Each summer solstice he would sneak under the roped-off areas, and encourage others to do the same and, in so doing, planting the seed for the giant party that now occurs there annually.

In 1998 the case of Pendragon was heard by the European Court of Human Rights in Strasbourg, his argument being that the exclusion zone around Stonehenge was a restriction of his freedom of thought, conscience and religion. He lost, but in 2000 full public access to Stonehenge was officially granted for celebrating the solstice.

Pendragon set up camp on the edge of the site after the 2008 summer solstice, to campaign for open access to the site all year round, much to the irritation of Wiltshire council, who claimed he was blocking a public highway. In the 2010 general election, he stood as an independent candidate in the Salisbury constituency over the issue. For him, the mass influx of visitors each year is anything but unwelcome.

"We didn't get a great sunrise [yesterday] but it was dry," he said. "Everyone seems happy with the result. It is great to see the stones being used in this way, as opposed to the usual manner with tourists being herded around." Before leading the ceremony yesterday, he spoke of the significance of the site for the druids: "Many stone circles, many wooded glades where we gather for different things, they are the churches. [Stonehenge] on the other hand, is the cathedral."

"The druids were amazing, and the morris dancers, but mainly it's just another excuse for a party," said Kristy Harlow, a screenwriter from Essex. "It's not like a music festival, though. The stones are the star of the show. In the morning light, they are extraordinary things to behold."

Yet the druids' love of the spot is far more cultural than historical. "Druids like to believe that they built it," said Cat Treadwell, a trustee of the Druid Network. "But it was there for a long time before they arrived."

In 1905, the Ancient Order of Druids performed a mass initiation ceremony there, in which they admitted 259 new members into their organisation, much to the ridicule of the press. The site, and date, steadily grew in significance, and their pilgrimages to the site grew in size, to the point where clashes with the police over use of the site became regular and larger in scale.

After the stones were roped off in the 1970s, English Heritage established a four-mile exclusion zone around them. On 1 June 1985, a "peace convoy" of 600 new age travellers journeyed to the 11th Stonehenge Free Festival, on squatted land beside the stones. It looked just like a carnival at first. The weather was sunny and music played as the convoy set off towards the ancient site. But the travellers were involved in a stand-off with police officers, resulting in dozens of injuries and hundreds of arrests. Reporters at what became known as "the Battle of the Beanfield" spoke of police in riot gear beating women holding babies with their truncheons. Cars were smashed and set on fire; 537 people were arrested, more than on any day since the Second World War.

For Ms Treadwell, the opening of the monument for one night of mayhem is an equivocal issue. "They are part of England; we should be allowed to access them. We've got the right to go there and to see the stones. And we still don't know how the stones got to where they are.

"But I am against vandalism and drunken rowdiness as it is detrimental to everyone. The stones are of great cultural and spiritual significance, just like Westminster Abbey. It is right for people to have access to these places. But then, people don't go to Westminster Abbey to take drugs or commit drunken violence, do they?"

However, the druids themselves are not completely impartial to a bit of what might be considered anti-social behaviour. "A woman in long robes grabbed my friend and said: 'Now is the time. You are my leader,'" said Natalie Mady, an engineer who attended the event with her student friends after she graduated in 2007. "And the RSPCA send people there to make sure no one performs any animal sacrifices."

Stonehenge and the Summer Solstice

Stonehenge has been an important site for sun worshippers for millennia, but the kind of celebration we see today owes much to the hippy movement of the 1970s.

In recent years, New Age groups, hippies, druids and party-goers have flocked to Stonehenge to celebrate the solstice, and the World Heritage Site has become a magnet for people seeking a "spiritual experience".

The first Stonehenge Free Festival was staged during the summer solstice of 1974. Five hundred hippies climbed a barbed wire fence to celebrate the event; 30 of them didn't leave for six months.

Police closed the site in 1984 after repeated clashes with party-goers. English Heritage, the monument's caretaker, began allowing full access to Stonehenge again in 2000.

Since then numbers have grown each year, and tens of thousands now travel to the site each year – some to worship the sun, others simply to have a good time.

Richard Hall