Witchfinders, by Malcolm Gaskill

In March 1645, the end of the year on the old Roman calendar, the astrologer William Lilly cast a horoscope. In the coming year he foresaw bloodshed and the planets making men "rapacious, cruell, treacherous". The country had been at civil war since 1642, so this was unsurprising. But that same month, in a small Essex town, something brutal and ferocious was about to be unleashed.

Magistrates pored over the transcribed confession of a crippled widow, Elizabeth Clarke, who had caused a tailor's wife to suffer tremors and delirium. Clarke - an obvious scapegoat, her own mother branded a witch - admitted belonging to a coven and conducting sexual relations with the devil. What followed lasted over two years, spread across East Anglia and sucked in up to 300 women and men of whom a third were executed.

This is a serious and scholarly account of the most chilling witch-hunt in English history. Waging war against this supposed diabolical invasion were John Stearne, a minor gentleman, and his more famous colleague Matthew Hopkins, the younger son of a clergyman. Both were part of the "elect" - Calvinists who believed they were chosen by God for salvation. Both came from Suffolk, which was seething with animosities between Puritans and Catholic recusants and royalists. In his high-crowned hat, cape and spurred boots, Hopkins was a man with a mission. Witches, he believed, had sent a bear-like spirit to try to kill him.

Gaskill deftly paints the scene in which this drama was played out. In East Anglia the rivers froze, food was scarce and the world seemed in turmoil while Parliament ruled without a king. Since 1563 witchcraft had been a statutory offence. "Witches,'' Gaskill writes, "were living symbols of rebellion against God and man, and to punish them was to strive for civil order.'' Working independently, Hopkins and Stearne rode from town to town by invitation, sometimes earning more in a week than a craftsman would in a year.

In King James's day, his book Daemonologie had served as a manifesto promoting witch-hunting. Since then cases of witchcraft had been isolated, with few prosecutions. But as the political crisis worsened in the 1640s, old fears returned. In the past, maleficium (where livestock or people were harmed or killed) had brought a witch to the scaffold. Now the conjuring of evil spirits was deemed sufficient.

Criminal law, however, demanded proof, which led to tests to expose the demonic pact. "Swimming" witches (the guilty floated, the innocent sank) was illegal but happened anyway. Accusers searched the accused for unnatural teats used by "familiars" to suck blood and found plenty in the form of warts, vaginal polyps, piles. The supposed imps or familiars were cats, rabbits and toads whose names - Vinegar Tom, Prickears, Susan - suggest the pets of lonely old people.

There were ways to force confessions. Frances Moore sat cross-legged on a stool, tied up for 24 hours without food or water. John Lowes, nearly 80, was deprived of sleep for days and run around till he was barely conscious. Delusion and guilt also played a part. The alleged culprits often swung from denial to defiance, as if by admitting to fiendish powers they would, perhaps, become powerful. In a society rife with superstition, it's not such a leap from "witches exist" to "maybe I am a witch". Demonic images of black dogs, and sex with cloven-hooved men peppered the confessions. Were they fed to the accused by the witchfinders, or ingrained in the collective unconscious?

Following Hopkins's death, the tide began to turn against the witchfinders, whose services were costly and questionable. Sceptics pointed to the unreliability of confessions exacted from frightened, vulnerable pariahs. Surely these were spiritual crimes to be dealt with by ministers and magistrates, rather than by self-appointed men?

Witchfinders is so densely detailed, sometimes you need to surface for air. This is not a light read, but it is fascinating. Gaskill presents a compassionate, measured view dispelling several myths along the way. Contrary to popular belief, unless witches had committed treason, in England they were never burned at the stake (as happened in Scotland) but hanged. Fiction and films have suggested the notorious Witchfinder General was lynched as a wizard. In fact, Matthew Hopkins died in his bed of pleural tuberculosis.

Far from depicting the witchfinders as sadistic bounty hunters, Gaskill argues they belonged to a different breed: sincere fundamentalists responding to a genuine and general unease. This is a story of fanaticism and zeal, but also of ordinary folk falling foul of their neighbours. To Gaskill our 17th century ancestors were not so different from "the provincial nobodies of the 20th century who engaged in genocide, demonstrating to the world the banality of evil". Terrible times make witchfinders of us all.