"I prefer to think of myself as belonging to the tradition of great British eccentrics," he said. "But if people want to see me as nuts, that's fine. I've found that being King Arthur allows me to stand up for serious causes."
Tomorrow the veteran supporter of green causes and opponent of roads will take on his most serious cause yet, when he becomes the first person to win the right to challenge the Criminal Justice Act in the High Court in London.
His lawyers will tell the court, which has granted him legal aid, that his religious freedom and right to assemble, enshrined in the European Convention on Human Rights, have been taken away by the powers the Act gives police to stop him celebrating the Summer Solstice anywhere near Stonehenge.
After violent clashes between police and New Age travellers at Stonehenge in 1988, the Druids found their traditional services stopped. An annual four-mile exclusion zone was thrown around the stones between 18 and 21 June, and public footpaths will be closed to the public.
This summer Mr Pendragon could be prevented from getting near Stonehenge by these controls. But even if he and his followers get through, they could fall victim to a new power that Michael Howard, the Home Secretary, has given police under the Act: to arrest people they consider to be holding "trespassory assemblies".
Police and Salisbury District Council have warned him he would be just such a trespassory gathering if he effects his plan to stage a service for about 30 followers on the verge of the A344, which runs close to the stones.
English Heritage, which controls the monument, allows Druids inside the area of the stones on the day after the solstice, when the monument is open to the public again, but when the sun rises, it will be closed to them and everyone else.
Mr Pendragon, who changed his name by deed poll in 1986 when he found he was the reincarnation of King Arthur, said: "It's like telling a Christian he cannot celebrate Christmas. Druids have never caused trouble at Stonehenge. We simply want to say a few prayers to the Sun and the Earth by a public road on our holiest day. Mr Howard seems to think that is a crime."
The civil rights group Liberty, which will represent Mr Pendragon, said the ban showed the police had "ominous" powers to prevent any assembly they did not like.
"The police and Home Office seem to believe that anyone holding a meeting on roads, paths, parks or common land can be treated as a trespasser because they don't have a specific right to protest on them," said John Wadham, Liberty's legal officer. "In the Stonehenge case, Druids are being banned from holding a religious service even though there is no evidence they will cause trouble, block a highway or annoy anyone.
"Police have always had the power to ban marches. Now, for the first time in British legal history they can prohibit meetings as well. This is a very important case. If we lose, we will go to the European Court in Strasbourg, where I think we will have every chance of winning."
Both Salisbury council and the police said they would fight the case. They said there was a risk of "serious disruption to the community" and that there could be damage to the monument.
Mr Pendragon is not a wealthy man, but he is determined to fight to the end to defeat their arguments, in London or Strasbourg. "I have no job and claim no benefits. But ever since I discovered I was a reincarnation I have found that I am fed when I am hungry and sheltered when I am cold.
"No one lives near Stonehenge, so we cannot disrupt the community, and I'm not even going into the stones, so I cannot damage them. My order is sworn to fight for truth and justice, and the Home Office will find out that we can fight very hard."