Reality TV in the UK was born in 2000 on a windswept Scottish isle. Now the show returns, but after years of increasingly outrageous series of Big Brother and its siblings, what will the islanders have to do to keep our interest?

In 2000, before Big Brother had ever been broadcast in the UK, 36 men, women and children agreed to pack up their busy lives and retreat to the treeless rock of Taransay in the Western Isles for a whole year. Keen to escape the trappings of modern life, the intrepid explorers were charged with filming their stay as they worked to create a sustainable community for the millennium - and Britain's first ever reality television show, BBC's Castaway.

Little did they know that their squabbles over budgets and animal husbandry, not to mention multiple emotional highs and lows, would change not only their lives but invent an entirely new genre of television.

On Friday, the former castaways will watch with interest as a second batch prepare to face what the BBC has billed as "a new shape, new twist but with the same underlying intentions". The tranquillity of the Western Isles is, however, not in jeopardy, for Castaway 2007 will come live from Great Barrier Island off the coast of New Zealand.

"They should have called it some-thing else as it's only going to be for three months, not 12 like for us!" jokes original castaway Philiy Page, on hearing they had plumped for warmer climes.

"It is hard for people to realise how intense it actually was on Taransay," she adds. "We didn't have newspapers or television and we shared one radio among us, so the only entertainment we had was each other."

London-born Page, who was 24 when she put her life on hold after hearing about the programme through her landlord, says the intense situation helped to create lifetime bonds among the castaways. "We couldn't have comprehended how close we would become. I suppose it came down to the fact we saw each other in the best and worst of times."

Many of the cast have since gone on to lead sustainable lives mirroring their experiences on Castaway. One couple even moved into an eco-pod, while others fled their city lives and bought homes on various islands.

Though Page herself has since returned to London to train as a TV filmmaker, director and producer, she maintains almost weekly contact with her scattered Castaway cronies through the "Taransay grapevine". She says: "My fellow castaways are like family, like the cousins you see at Christmas. We still send cards, chat on the phone and meet up when we can."

Much of the programme's appeal - at one point it amassed more than nine million viewers - was the raw emotion caught on camera by the group as they faced up to life on the windswept island. Page says: "I felt so privileged when I stepped on to the island. The start was really difficult as the storms had damaged our eco-pod homes so there were builders everywhere.

"I got a bit down with all the arguing that went on, but when May Day came along the mood changed for me. This was the first time we really got together, the weather was absolutely gorgeous and it really felt like the community would work.

"The good thing for us was we were filming so we could turn off the cameras whenever we liked. There is a lot the public never got to see - mainly parties with everyone drinking home brew and swearing about the production company."

Where Big Brother and Love Island producers would be kicking themselves at missing out on any such raucousness, former Castaway producer Paul Overton remains immensely proud of the unique way in which the events on Taransay were filmed.

"All the layers - one castaway as a designated camerawoman, video diaries, and then the crew filming big events - it was quite innovative, and I have still not seen anything totally comparable," he says.

"I think it was a bit more innocent than today's reality TV, which tends to be quite ruthless, but we did set out with a purpose to reveal whether a sustainable community could be created in the millennium."

Overton and fellow producer Chris Kelly began their preparations for the show on April 1, 2000, and, reflecting on the pressures of producing more than 25 hours of footage, he believes the day may have been more symbolic than he first realised.

"The scale of the project was nuts," he says, "and it felt at the start like we were building a mini village. I am a producer but I soon found myself seeking out builders, arranging boats and chatting to landowners and environmental health guys. It was absolutely the first of its kind. The practicalities were insane but once we had started we were in it for the ride."

And what a ride it was, including meningitis scares, arguments, castaways seeing their belongings washed into the Atlantic - and, of course, the adventures of a certain Ben Fogle and his black labrador, Inca. Throngs of women were glued to the screen as posh crumpet Fogle, now a television presenter and part-time adventurer, lived out his boyhood ambitions to shear sheep and explore uncharted lands.

Fogle, who was picked on by some castaways due to his popularity with the public, was taken aback by the interest paid to him. "I did realise something strange was happening when I started receiving lots of letters, marriage proposals and even a few pairs of knickers in the post. I found it all a bit surreal," he says now.

Love was definitely in the Taransay air, with two children conceived on the island (off camera); a litter of puppies born; several honeymoons (not during the year) and even one Castaway marriage. In 2004, Overton wed castaway camerawoman Tanya Cheadle, before retiring to the island's former school house for their honeymoon.

Overton, who tactfully recounts meeting his wife as his favourite Castaway moment, says of the chosen setting: "Harris is still one of my favourite places, it is gobsmackingly beautiful. Tanya and I will hopefully be visiting again this year."

However, it wasn't all roses and chocolates. Before Leo Sayer or Donny Tourette had ever got their knickers in a twist and legged it from the Big Brother house, seven of the Castaways quit throughout the year. One departee, Ron Copsey, successfully sued Lion Productions for their misrepresentation of him, including "did he/didn't he" scenes of chair throwing (he didn't).

Ray Bowyer, the first to leave, was on the front page of every UK newspaper after he led the press a merry dance round the Hebrides. Bowyer escaped from a car belonging to the Daily Mirror, opting instead to share his story with the Stornoway Gazette. Iain MacSween, who at the time was just four days into his job as a junior reporter, still has vivid memories of his Bowyer scoop.

"He jumped out of a taxi and ran up to our receptionist saying, I'm the one who's escaped, I want to speak to a reporter.' Quick to seize the opportunity, I paid his taxi fare, shut the office door, and got the story," MacSween recalls. "He was stinking, he'd tried to have a shave in the Co-op but you could have cut the air with a knife. That said, it was a dream come true. Meanwhile, the rest of the press were running about totally oblivious to his whereabouts."

For action-hero castaway Mike Laird, there was no way he was not going to "do the 365". Laird, now working in Sutton as a risk manager for an insurance company, believes his Castaway experience was 95% good.

He says: "I went for a life opportunity - it was something different, something new. I was a single guy so I put my life in storage and headed north.

"Doing the 365 became a big deal. It might have been a concocted environment but, day to day, it didn't feel that way. It was as real as it could be, slaughtering pigs, shearing sheep and building deer fences."

During his Taransay stay, Laird went on a "summer holiday" - a survival project away from the rest of the community, where he built a shelter from driftwood and stones. "All I had was a bag with some kit and a bloody huge knife. I ate what I could find on the beach, or picked up an unfortunate sheep - that didn't go down too well with the vegetarians.

"I was quite a manic person when I went in but I left much calmer and I became more tolerant of people and accepting of their differences."

Since the castaways' departure, Taransay has been returned to its original state and purpose, with the eco-pods removed and some 900 sheep returned. For Hebrideans, the show is remembered with a mixture of fondness and shrugged shoulders.

Bill Lawson, a genealogist from Harris, was not overly disappointed to hear the new series won't be returning to the Hebrides. "I found it all too contrived," he says. "I saw it as a daft idea at the time, starting in winter like that and I must admit I chuckled when I heard they are off to New Zealand for the next one. If nothing else, it shows they have learned their lesson."

But Taransay owner Angus Mackay may beg to differ. His offer of seasonal trips to stay on the island have taken off. He says: "It was an exciting time and it certainly put us on the map. We get a lot of bookings from people going across because they remember Castaway and want to see where it all happened."

The new series of Castaway will maintain a Scottish presence in the form of Dundee-born presenter Danny Wallace, but otherwise may appear largely detached from its roots. For a start, apart from being on the other side of the world, Great Barrier Island is some 20 miles longer than wee Taransay and already has 900 inhabitants. And if the castaways do choose to leave prematurely, they won't need to don swimming costumes to reach restaurants, shops and pubs.

But creators Lion TV and the BBC have been at pains to stress a similar purpose to the original, and carried out a rigorous castaway selection process to whittle down the 2500 applicants to the lucky final handful.

As on Taransay, the recruiters have been aiming to reflect all aspects of British life. Though the identities of the chosen participants remain a closely guarded secret, the chosen few include a member of a Goldie Lookin' Chain tribute band, a former page three photographer and a woman who once refused a £10,000 offer to spend a weekend with someone.

Dr Cynthia McVey, the resident psychologist for the original Castaway series, interviewed the first applicants in 2000 and knows fame was far from their minds. McVey, a psychology lecturer at Glasgow Caledonian University, says: "The castaways went because they wanted to experience a life without the modern trappings of society, not because they wanted on TV. In fact, sometimes the producers had to remind them they were part of a television programme.

"Now people know that, when you sign on the dotted line, they can show the funny bits and make you out to be a comedian or they can show you always moaning. Seventy percent of the time you are happy, but they can choose to only show your moans."

Despite this, McVey isn't critical of the producers. She adds: "We can say what we like about production companies and editing teams but they are only putting together what the increasingly desensitised public want to see. It is being driven by us, the viewers, so we can't always get on our high horse.

"The Scottish Castaway was a remarkable project and it led to much academic work on ethics and group formation. It was quite a serious programme; more of a documentary in style than a reality TV programme."

McVey, who is also still connected through the "Taransay grapevine", is looking forward to watching the new Castaway series, though she admits there were some hairy moments the first time round.

She says: "In the middle of the night I would wake up thinking, I hope they don't kill themselves on that island'. I thought the castaways were remarkable people. It was just an absolutely terrific programme, a real step into the unknown, and for that you have to give credit to Lion TV and the BBC. It will take a lot of courage and a big deep breath to try to do it again."

The new series of Castaway is on at 9pm this Friday on BBC1; Castaway: The Last 24 Hours follows at 10pm on BBC3