Who are the killer clowns and why is it happening here?

It's a craze that has left billions of sane people baffled and has resulted in scores of victims being scared out of their wits.

Britain has been invaded by an army of clowns who are stalking the streets and terrorising children and adults with knives.

In one shocking incident on Friday, a “killer clown” with a knife chased two children aged 11 and 12 to school in County Durham.

And as this video shows, one reveller chased off a ‘killer clown’ who was armed with a hammer in Devon on Friday night.

Dozens of similar ordeals have been reported to police, leading to officers from Scotland to Essex to warn that anyone caught clowning around will be arrested.

There have also been sightings of masked clowns at a fast-food restaurant in the Birmingham, lurking in an underpass in Leeds, wearing a blood-stained poncho in Manchester and riding a mobility scooter in Sheffield.

Girls were playing netball at a school in North Shields when a prankster in a red wig and blue jumpsuit scaled the fence and sparked panic.

Creepy clowns have also been spotted in people’s gardens and peering into their windows.

The so-called “killer clown” craze appears to have been inspired by terrifying pranks in South Carolina, where police first received reports of clowns lurking near launderettes and trying to lure children into the woods.

It is unclear what sparked the craze, although some claim it may be part of a horror movie publicity stunt or an elaborate hoax.

Since then, clowns have sparked thousands of copycats across the US and worldwide, with police in Australia also issuing stern warnings to would-be clowns.

The craze has also angered professional clowns, who work in circuses and as children’s entertainers, and who have told the i newspaper that the “idiots” are bringing the “art of clowning” into disrepute.

“It’s incredibly frustrating,” said Rob Bowker, a spokesman for Clowns International, the world’s oldest clown club.

“These people are not clowns. They are just idiots wearing clown costume. It isn’t funny.”

Mr Bowker, who works under the name Bibbledy Bob, added: “Clowning is an art form and it takes years to learn. These people are hijacking the costume and scaring people.

”Children have nothing to fear from real clowns. They only want to make people smile. These people are nothing to do with us.“

Clowns have been around for thousands of years – dating back to the court jesters of Henry VIII and beyond – and were traditionally a vehicle for satire.

The word ”clown“ first appeared when Shakespeare used it to describe foolish characters in his plays.

The now familiar circus clown has its origins in the 19th century.

Ann Featherstone, a research fellow in drama at the University of Manchester and an expert in Victorian clowns, told i: ”There is a darker side. There have been nasty clowns throughout history.

“There has always been a suspicion about clowns. It’s to do with the grotesque mask and the make up, which emphasises the nose and the mouth and has no expression. We don’t know what clowns are thinking or what they will do next.”

Professional clowns say the “demonisation” of clowns started in the 1980s, when authors and Hollywood movie directors began depicting them as villains in horror stories.

Perhaps the most feared of all fictional clowns is Pennywise, the red haired clown with razor-sharp teeth, who appeared in Stephen King’s 1986 novel It and which was adapted for television in 1990.

One professional clown told i that the irrational fear of clowns – officially known as coulrophobia – originates from this period and is less seen in today’s children who have not been brought up with these movies.

But a recent survey found that clowns came in first place as the creepiest profession, followed by taxidermists, sex shop owners, funeral directors and taxi drivers.

Freaky Clowns first took on a sinister persona in the 1970s when serial killer John Wayne Gacy, who was known as the Killer Clown because he worked as a clown at children’s parties, murdered 33 young men in Chicago.

“In many ways, clowns combine a perfect storm of freaky things,” said Professor Frank McAndrew, a psychologist at Knox College in Illinois, who has carried out the first empirical study of creepiness.

Speaking to i from the US, he said: “You cannot tell what they really are or what they are really feeling, and they have an association with serial killers in real life and in the movies.”

He added: “The killer clown has the perfect ingredients for an urban legend. They can occur anywhere and there probably enough copycats keep it going.

”I’m skeptical that there are not nearly as many actual incidents as there are have been reports.

“I’m betting almost all of them are young men who love the testosterone rush that comes from seeing people run away. Many of these incidents originate from an unfortunate combination of alcohol and to look brave in front of friends.”

The killer clowns show no sign of being vanquished quickly from Britain, with thousands of shops now selling clown masks for Hallowe’en.

Two horror films featuring clowns are being released this year. The hated Pennywise will reappear next year in a movie remake of It.

Stephen King has appealed for calm. We spend our lives spreading fun, laughter and happiness, but these people are nothing to do with us. It’s nasty people running down the street with knives. It’s horrible and it’s frightening.

Mattie Faint, the Clowns Gallery and Museum In one of the latest incidents, a man was approached by a clown armed with an axe in a cemetery in Leicestershire.

“I have never been so terrified in all my life,” the victim said. “It’s really sad,” said Mattie Faint, who has been a professional clown for 45 years and is director of the Clowns Gallery and Museum in London.

“This issue comes up time and again when Hallowe’en costumes start appearing in the shops.

”We spend our lives spreading fun, laughter and happiness, but these people are nothing to do with us. It’s nasty people running down the street with knives. It’s horrible and it’s frightening.“