Cecil Williamson was a former film producer with a personal interest - perhaps practical, perhaps just curious - in folk magic. He believed in the cunning folk, the village wise women and wise men of pre-industrial Britain, and he wanted to preserve their material culture before it disappeared. In 1951, the year Parliament repealed the Witchcraft and Vagrancy Acts that had criminalised the practice, he opened the Folklore Centre of Superstition and Witchcraft in a dilapidated mill in Castletown on the Isle of Man. He hired the prominent Wiccan Gerald Gardner as "resident witch" - Gardner needed a stage on which to promote his new religion, Williamson needed publicity. The arrangement worked until it didn't. The two men fell out over Williamson's increasingly sensationalist displays. In 1954 Gardner bought the Castletown property, renamed it the Museum of Magic and Witchcraft, and Williamson took his collection back to England.

What followed was a small, sustained, and largely unrecorded persecution. In Windsor the museum opened for the 1954 tourist season and did well financially, but local opinion was against it and Williamson moved on. He chose Bourton-on-the-Water, a pretty Cotswold village. There the persecution turned active: slogans painted on walls, dead cats strung up in trees, threats. The museum was finally damaged in an arson attack. Williamson, hardly a young man and now twice run out, looked for somewhere far from English market towns. Boscastle in 1960 was a faded fishing village on a difficult bit of coast with limited road access, plenty of slate, and a tradition of leaving outsiders alone. It was perfect.

Williamson's interest was always practical folk magic - what he called the "wayside witch" - rather than the ceremonial magic of Aleister Crowley or the new ritual structures of Wicca. The museum's centrepiece is still "Joan's Cottage," a reconstruction of a nineteenth-century cunning woman's room, with a mannequin surrounded by drying herbs, divination tools, and the small specific objects of bewitchment and counter-bewitchment. The museum holds Crowley's ritual chalice, talismans made by Gerald Gardner, and ritual swords and an altar slab from the Wiccan elder Alex Sanders. The collection grows year by year as practitioners leave their working tools to the museum in their wills. The anthropologist Helen Cornish, who studied the museum and its visitors in the late 1990s, found that the British occult community treats Boscastle as something close to a place of pilgrimage.

In 1996 Williamson sold the museum to Graham King and Liz Crow, who finalised the purchase at midnight on Halloween. King was a Hampshire camera manufacturer who had discovered the museum was for sale in a newspaper article. He and Crow began a quiet reorganisation. They removed the more sensationalist displays - a partly clothed female mannequin laid on an altar to represent the Black Mass, for instance. They also began doing right by some of the human remains in the collection. Joan Wytte, a deaf woman who died in Bodmin Jail in 1813 under accusations of witchcraft, had been on display at the museum for years. King organised her burial in a piece of local woodland in 1998. Three years later, in August 2004, the Boscastle flood tore through the village and damaged the museum, sweeping part of the collection downstream. The museum closed for repairs and reopened in March 2005. In 2013, on Halloween, King transferred the museum to designer and curator Simon Costin and his Museum of British Folklore. "It won't change at all," Costin told the Cornish Guardian. Mostly, it hasn't.

It is easy to mistake the Museum of Witchcraft and Magic for camp. It is not. The collection is one of the most serious anthropological archives of British folk belief that exists. The artefacts come from the actual practice of actual people - cunning folk who were the village's first port of call when the cow stopped milking or the child stopped sleeping, healers and curse-removers who occupied a real role in a world without GPs and licensed pharmacists. Williamson understood that this knowledge would not survive its practitioners unless someone collected the objects and the stories. He was right. Most of it would have been thrown out as junk. What the Cotswold villagers feared, with their painted slogans and dead cats, was something that had largely vanished from their own villages a generation earlier. The Boscastle museum is one of the few places left where it can still be looked at honestly.