by Kev Geoghegan
Entertainment reporter, BBC News
The shot of a terrified film-maker's tearful apology to her family has become one of cinema's enduring images
In 1999, The Blair Witch Project set box offices alight, becoming one of the most profitable movies in cinema history.
Costing less than $100,000 (£60,000) to make and presented in documentary style, the low-budget horror flick went on to make $250m worldwide, thanks to an early online viral marketing campaign and good old-fashioned word-of-mouth.
Ten years on, the film - which recounts the disappearance of three young film-makers setting out to investigate a local witch legend in rural Maryland - still has the power to shock.
The film's doomed cast Josh, Heather and Mike
"We had this very basic and very primal foundation, which was fear of the woods, I mean, who isn't afraid of the woods at night?," says Eduardo Sanchez who, along with Daniel Myrick, wrote and directed Blair Witch.
He continues: "To me, the woods at night is a place where humans maybe used to feel at home there, but I think that now we fear them.
"It transmits not just culturally, but to people of all ages."
The story began in 1993, when fellow film students Sanchez and Myrick drafted a 35-page outline with much of the dialogue to be improvised.
The makers produced an eight-minute documentary of the mythology of the Blair Witch as fact, along with mocked-up newspaper clippings and interviews.
The eight-day shoot began fours years later in 1997 at the Seneca Creek State Park in Maryland.
The actors, Heather Donahue, Joshua Leonard and Mike Williams had been given a crash course in operating their cameras.
During the day, the cast were guided to filming locations with directions delivered in milk crates and were given ideas to improvise dialogue.
Hidden from view, the producers terrorised the cast during darkness, depriving them of food and sleep.
Sanchez says the shoot was a "very intense ten or eleven days".
"The whole shoot was pretty hectic but really fun.
"We all knew that we were doing something special, at least the way we were shooting it, and we knew that we would probably never make another movie like this."
The technique of using hand-held "shaky" cameras in Blair Witch have since become a horror staple, with films including Cloverfield and Quarantine taking the lead from Myrick and Sanchez.
Although in use long before Blair Witch, Myrick says the technique is now more accepted by mainstream audiences.
"Everything from news channels to documentaries use hand-held cameras and I think the viewers perceive it as truth: 'I'm watching something that's truthful because it doesn't look produced and premeditated.'"
After eight months in post-production, trimming 19 hours of footage into a digestible 90 minutes, The Blair Witch Project was shown at the 1999 Sundance Film Festival.
It was picked up by film studio Artisan for a reported $1.1m (£661,000) which helped fund a new type of internet marketing campaign to suggest the film was a real event.
Very early on in the film's development, Sanchez created a website which purported to be the definitive guide to the myth of the Blair Witch.
Now in an age when most Hollywood blockbusters use some kind of online viral marketing, Sanchez acknowledges he was breaking new ground.
Actor Mike Williams and director Eduardo Sanchez hang out in the basement
"I was the only one with web-building experience and also, I didn't have a girlfriend at the time so I had a lot of time on my hands.
"We had created this whole mythology and I just kept massaging it and building more details into it.
"Really for us, it wasn't about creating this whole new way of marketing films - people are on the web asking about this movie, how else are we going to get it to them?
Release and reaction
The film was released on 30 July 1999 and went on to earn nearly $250m, netting its makers a modest profit which they are reluctant to divulge.
"We had to fight for our piece of the pie but ultimately we did okay," says Myrick.
"It was nice to be able to pay back the people that believed in us like our families and friends."
But peaking so early left its mark on Sanchez, who took a self- imposed "retirement" which lasted several years.
"Part of my semi-retirement after Blair Witch was me dealing with my personal demons like, 'How the hell am I going to follow this movie up?
"To use an American analogy, it was like winning the world series on your first time at bat."
Desperate to cash in on the worldwide Blair Witch buzz, a sequel was hastily prepared at Artisan, directed by documentary-maker Joe Berlinger and released in 2000.
Although turning a profit, Book of Shadows: Blair Witch 2 was soundly derided by critics the world over and was nominated for five Razzies, Hollywood's equivalent of a slap in the chops.
"We felt a little betrayed because we wanted to let the Blair Witch hype die down a little because it was so out of control and there was a bit of a backlash," says Myrick.
"But they wanted to strike while the iron was hot and they went ahead and made the movie for what we thought were all the wrong reasons.
"We felt that the story of that movie broke the mythology."
Sanchez agrees: "We don't feel too responsible for that movie, because we had very little to do with it once we stated our objection to where it was headed.
"At the same time, it does have the Blair Witch name on it."
Now, ten years on from the original, Sanchez and Myrick - whose subsequent careers haven't quite matched the early zenith of Blair Witch - are working on another sequel.
Sanchez admits they are still undecided how to proceed with the project, whether to stick with the grittiness of the first film, or make a more polished and more obviously expensive sequel.
"Ideally, each Blair Witch film would be a completely different kind of movie,", he says. "We've thought about doing a film that takes place in the late 1700s and looks like a [Stanley] Kubrick movie with gritty looking people and lighting.
"But now, we're thinking about going back and and seeing what happened directly after the first film finished.
"I think it will have some kind of video element in it, but it won't be a first person hand-held movie."
With the fate of the original characters an unsolved mystery, it is unlikely the actors will also return for the film.
Myrick says: "I talk to Josh quite regularly and Mike Williams as well. Actually, he had a role in my last movie.
"Heather, I haven't seen in years. The last I heard, she had got out of the business and gone up north and is living on a ranch somewhere.
"Maybe she's still traumatised," he adds.