When I was growing up in Edinburgh in the 1970s, Hallowe’en involved adults organising fun activities for excitable children. But look around any British towncentre tonight and you will see a bizarre transformation. Pubs are festooned in ghoulish decorations, respectable restaurants have witches’ broth on the menu and nightclubs are even more than usually playing host to the living dead.

Not all of these revellers are students. For Hallowe’en has become a party at which you might easily rub shoulders with a barrister or investment banker. At almost any time in England during the last 200 years, child-free parties at which consenting adults dressed up as witches and warlocks would have been regarded as eccentric. Now they are all the rage.

Some may pretend that they are reviving the ancient Celtic rites of Samhain, but Hallowe’en’s current format is essentially American. Its couture is Hollywood. At most, Britain’s contribution is a derivative off-the-peg fashion from Hammer Horror.

Still, Hollywood must have got the idea from somewhere. We can be sure it did not come from English immigrants. Protestants do not believe in purgatory or praying to saints. Thus the medieval custom of praying at Hallowmas to the beatified in Heaven and, on November 2, for the souls of the dead in purgatory by pealing bells and lighting candles, was suppressed after the Reformation. In its place Parliament sanctioned public celebration of the Gunpowder Plot’s failure on November 5, a rare occasion of a secular festival achieving long-term popularity in Britain. It even became a semi-religious rite: it was included in the Book of Common Prayer until 1859.

This Protestant tradition was carried across the Atlantic. Late 18th and early 19th-century North American almanacs often marked Guy Fawkes Night (even after the War of Independence) but did not mention Hallowe’en.

It was Irish migration that brought to the US a variety of folk myths and merrymaking to October 31. More often it was with talk of fairies and the “good people” rather than sinister demons. Scottish migration, meanwhile, brought Caledonian customs to Canada. Renderings of Robert Burns’s Tam o’ Shanter and Hallowe’en kept the memory of dancing witches fresh in Scottish culture.

When the ghoulish element in Hallowe’en supplanted harmless superstitions long associated with the day — games designed to foresee who a maiden might marry and children ducking for apples — is open to debate. By 1900 US college freshmen had turned it into an evening of high jinks, and only by the 1920s were witches’ hats and black cats a standard part of their decoration. Hollywood adaptations of Gothic horror novels did the rest. But being trick or treated by your bank manger, now that is new.

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