Hallowe'en: How the hell did it get here and what does it say about us?

The doorbell goes. Again. A cute little kid in a devil's outfit grins and holds out his hand. "Trick or treat, mister?" Oh really? What can a tousle-haired boy with freckles do for a trick? He can't be more than eight, but he's not impressed with the treat. "What's this?"

It's fruit. A satsuma. "You're having a laugh," booms a deeper, rougher voice from the shadows. A big brother. "Don't give him that crap."

There is nothing else. No chocolate, no sweets, just a satsuma: juicy, nutritious and cheap. Take it or leave it. They leave it, with a few choice words no eight-year-old should know. And so we wake up the next day to find eggs splattered all over the front door and the car doused in flour.

What has happened to Hallowe'en? It used to be a gentle, home-made affair. If you didn't like it you could ignore it. Now, suddenly, there are yobs in Scream masks hammering at the door and the supermarkets are full of pitchforks, bat cakes and dancing Frankenstein's monsters. Where did it all come from? What dark forces are at work? What does it tell us about ourselves?

The answers mix money with glamour and fear, always a potent brew. The money is in the supermarket tills. Proof that the sudden rise of Hallowe'en is not the product of a fevered imagination comes from these figures: just five years ago we spent, as a nation, about £12m on fake fangs and devil horns. This year that is expected to top £120m.

Such things do not happen by accident. The supermarkets have deemed it should be so. Woolworths says that at the turn of the century customers who had been to the US - where they will spend more than $3bn on Hallowe'en this year - started asking why they couldn't have blood-dripping candles too?

So Woolworths put in 50 Hallowe'en lines. A year later the range included 100 goods. This year there are 224. One reason for the boom, spokeswoman says, is that parents afraid of fireworks are choosing to throw Hallowe'en parties instead. "Some children don't know who Guy Fawkes is."

The past seven days have been the second-busiest shopping week of the year. Adults are falling for Fright Night, say the supermarkets. Emma Felton is one such adult. She will marry Will Sparrow tomorrow in Bedfordshire wearing a top, trainers and cloak in pumpkin orange. Mr Sparrow will wear an orange suit. Guests have been asked to bring witch's hats and broomsticks. "We both love Hallowe'en," says Ms Felton, unnecessarily. Adult costumes are suddenly a huge seller. "There is a real trend for young, single people to go to fancy dress parties," says Julie McGuckian of Tesco. "People feel much braver chatting someone up if their face is covered." Tesco researchers found our Hallowe'en much gentler than the American version. "They have a real horror side to it. We would rather have glow-in-the dark skeletons or a bit of glamour ,like our Sex Bat dress."

Ah yes, the glamour. The costumes and toys on the supermarket shelves are haunted by the ghosts of Bela Lugosi, Boris Karloff and Carolyn Jones as Morticia Addams. These are the reference points for Hallowe'en designers, with modern Hollywood icons like the Scream slasher. But it was all just bubbling away quietly in Britain until the Nineties, when viewers saw Hallowe'en specials on imported TV shows including The Simpsons and thought they looked fun. Then came Harry Potter. Since JK Rowling published the first of six novels (so far) in 1997, she has sold more than 200 million books, inspired four films, made a fortune and turned countless young people on to the wonders of witches and wizards, potions and spells. The dark side made cute gave so much impetus to the revival that this could almost be renamed Harrye'en. Rowling decided to let Potter grow up, increasingly aware of the dangers of the world. Which brings us to fear.

Not fear of the hooligans at the door, although they are a pain. Police found a dramatic rise in anti-social behaviour around 31 October so they will use fixed-fine penalties of £80 and asbos to stop the worst offenders. They are also offering posters saying 'Sorry, no trick or treating here'. Which will make a nice target.

No, the fear behind Hallowe'en is something much older. Ancient, even. Its roots are in Samhain (pronounced sow-in), the Celtic festival to mark the end of the festival and the start of a new year on 1 November. The borders between worlds were felt to dissolve: the dead moved freely among the living, and the living were free - if they dared - to ask them what the future held. There were bonfires, sacrifices and costumes made from animal heads and skins; and after the festival they used the sacred fire to light their own hearths and keep away the spirits.

Trick or treating was started by Irish country boys who visited farmers on the night before Samhain to collect provisions for the celebration. They played pranks if refused.

The Christians tried to remake Samhain, as they did so many other pagan festivals. In the 7th century Pope Boniface IV introduced All Saints' Day, also known as All Hallow's Mass. The night before was All Hallow's Eve, or Hallowe'en. Later the Church added All Souls' Day, 2 November, when prayers were said to help the faithful move from purgatory to heaven. There were bonfires, parades and costumes of angels and devils.

We think of Hallowe'en as an American invention, but it was the Irish who took it to the US during the Great Famine. Instead of hollowing turnips for lanterns as they had back home, they used pumpkins. The phrase 'Trick or Treat' was first used in America in the 1930s, a time of Hollywood monsters, when the commercialisation of the festival began.

Now American-style Hallowe'en has been reimported to the British Isles. There are 30,000 pagans in Britain, who now know how the Christians felt about having a sacred festival turned into a spending frenzy. The Christians don't know what to do. Some churches boycott this devil worship, some organise other events, some sheepishly let their children take part.

The Church of England puts up the Bishop of Bolton as its expert. "Hallowe'en is not a dangerous occult celebration in origin," he says, "although it has picked up some of those traits over the centuries."

So what does this tell us? That we are easily led by the supermarkets. That any excuse to party (or throw eggs) will do. That we have a fatal passion for trashy US culture.

Or maybe there's more to it than that. Professor Ronald Hutton of Bristol University, an expert in pagan culture and ritual, believes our Hallowe'en is less extreme than America's because we are less dominated by religious belief.

The surprising thing is that this fake-blood-spattered jolly, trashy ghoul-fest on which we are spending so much money may be closer to the origins of Hallowe'en than anything we have had before. There are many reasons to be afraid in the modern world, and one ancient reaction to fear is to party.

"The celebration of Samhain was about facing up to the coming of winter, which was the most frightening of all seasons," says Prof Hutton.

"It was about facing up to coldness, darkness and death: but about mocking the things that frighten you, so that you feel less afraid. That is still what Hallowe'en is really about."

ADULT COSTUMES

The number of adults hiring costumes at this time of year has more than doubled, according to industry estimates, although the rise has been so sudden that nobody knows exactly how many costumes are going out. The season has been brought forward by at least a month. Hiring a Victorian vampire outfit for a week costs £40-£60 from Mad World, which has around 35,000 at shops in Gatwick and the City of London. Bought from second-hand shops, theatres and suppliers in Europe and America or made in-house, costumes can cost £2-£300 to buy and usually have a life of about four hires before they get tatty.

CONFECTIONERY

The treats, party bags and snacks we hand out on 31 October are worth £4 million to the shops. Graveyard Rocks - small, round candies in ghoulish colours - are typical of supermarket offerings at this time of year. Individually wrapped in cellophane, there are 20 of them in a bag that sells for 89p. Like most of the sweets in the Hallowe'en aisle at Asda, they are made in Chinese factories and imported to this country by Candy Creations, a specialist company based in Glenrothes in Fife, Scotland. The company also operates in South Africa and Australia. Ingredients include sugar, glucose syrup and the E numbers 104, 110, 129, 133 and 171.

RETAILERS

Five years ago we spent a total of£12 million on Hallowe'en goods, treats, outfits and toys. Since then the total has doubled every year, and is expected to be well up on the £ 100 million reached in 2004. Woolworths says 31 October is now the third most lucrative festival of its year, behind Easter and Christmas and ahead of Valentine's Day and Bonfire Night. Other stores disagree about the order but agree Hallowe'en has left Guy Fawkes for dead. Tesco says adults are also seizing the chance to dress up and party: besides sexy witch outfits, sales of beer, wine and spirits are up 27 per cent.

CHILD COSTUMES

When supermarkets began to push Hallowe'en five years ago they found that dressing-up kits for children sold in their

tens of thousands. That is still true, as parents tend to hire outfits for themselves but buy for the little ones (making a witch's hat out of cardboard is out of fashion). The Devil Girl costume (not shown) sold by Woolworths for ages 3-4 at £9.99 includes a simple vest top, skirt, horns and a wand. Woolworths will not reveal its supplier but many supermarket costumes are made cheaply in the Far East, so profit margins are high.

ANTI-SOCIAL BEHAVIOUR

Last year the number of anti-social behaviour orders (Asbos) issued at Hallowe'en doubled to 786. This time, police forces are setting up special squads to target likely offenders. They will issue £80 fines for public disorder, including throwing flour or eggs. Half of the 4,649 Asbos issued since 1999 have gone to children aged between 10 and 17.

PUMPKINS

The seed for your lantern was planted in March and harvested in September. At Oakley Farms in Wisbech, Cambs, they have gathered up more than one million pumpkins this season, so the overall figure for the industry will certainly be up on last year's record. The carvers are mostly the American varieties Mars and Harvest Moon. A pumpkin that sells for £2 might cost £1.50 to produce, so profit margins are slim but volumes are large. Oakley Farms began with one acre of pumpkins 15 years ago, and sold produce to US air bases. Production has soared by 700 per cent in seven years and it now has 188 acres.