House walkout shocker: Anna, who hasn't left her house for the past three weeks, thinks about going outside as she is getting bored. But after having a sleep on it and talking it over with her housemates, she decides to stay put after all.

If someone was to tell you this was the story of the week, you might think they were mad. If they were to describe it as a "bombshell" which sent ripples of anxiety through the ranks of the viewing public, as at least one publication did this week, you might just scratch your head in bemusement. But then you must be one of the few people yet to have encountered Big Brother, the Channel 4 docu-soap/game show phenomenon which has beat a path to the top of the TV ratings in the UK where - like here - it has cultivated an obsessive following.

The Anna in question is Anna Nolan (29) from Crumlin in west Dublin, who is the strong favourite to become the first female winner of the show in any of the countries in which it has been broadcast.

For the uninitiated, she was one of 10 entrants starting out - seven by the time you read this - placed under 24-hour surveillance last month in a purpose-built house on the London Docklands. As with the other TV ratings phenomenon of the year, Who Wants to Be A Millionaire?, the concept is blindingly simple and has made its investors very rich indeed. Each week, the contestants nominate two people for eviction, and the viewers vote on which one should leave until one winner is left, £70,000 richer.

To call the flatmates contestants, however, is something of an understatement. These aren't the sort of nervous souls you'd find sweating under studio lights on Winning Streak. They're brash, loud-mouthed exhibitionists, drama queens and fledgling celebrities for whom the competition is only a stepping stone towards stardom.

Some - like Thomas McDermott (31) from Greencastle, Co Tyrone, who was nominated for eviction this week - have a background in acting. Others, like Anna, have expressed a desire to work in the television or music industries. In a possible premonition of her future career, she told her flatmates when she awoke last Wednesday she had just been dreaming she was presenting Top of the Pops.

Not necessarily a fanciful thought when one considers the two candidates already dumped from the show have been offered lucrative promotional deals worth up to £100,000 and are charging £10,000 a pop for interviews (Pat Kenny take note: Anna won't come cheap for the Late Late). The winner of the German version of the show screened earlier this year has become a pop star. His first single is imaginatively titled Gewinner (Winner). Similarly, Bart and Sabine, contestants on the original Dutch show, are now TV stars in their own right, their notoriety earned by sleeping together under the surveillance cameras.

Anna may not have to do anything so dramatic, however, to scoop the top prize. Her sheer niceness has made her the bookies' favourite to win, her odds shortening this week to 2/1 after modestly declaring to the Big Brother video diary: "I'm not that interesting and I don't think I will be missed when I go."

Not interesting? Her CV reads like a good airport novel. Born into a family of five sisters and a brother in Dublin in October 1970. Educated by Loreto Sisters in Crumlin, excelled at basketball and music, went on to coach local children at the Naomh Mhuire basketball club, which has since closed down. After school, she enrolled in the Loreto Order but left after a year because, she said, "I thought religious life was too regimented and I had started to have crushes on fellow nuns."

Not long after, she left her native city to live in London and fell in love for the first time - with an Irish girl. She has worked in a maternity hospital and a women's prison and is currently employed as an office manager.

A Mary Black fan who describes her mother as her hero for raising seven children and then getting a degree at the age of 59, Anna has stamped her identity on the Big Brother show by falling into the role of confidante-in-chief. Her sympathetic soundings have made her the most popular woman in the house.

A perfect example of her niceness presented itself this week when she was asked to name the parent who had influenced her most. Like the aunt who couldn't say which of her two nephews' drawings was best, Anna sighed that "they've both influenced me equally in different ways . . . my Dad worked really hard to bring up seven kids, worked like `money' work, but my mother worked really hard at home bringing us all up . . . I couldn't choose one."

Ah, Anna! Some might say she is just too nice to be true.

And they might have a point because the thing about Big Brother and its contestants, Anna included, is that you never know exactly how much of what goes on is genuine and how much is just an act for the cameras.

Already one of the cast, Nicholas - the jovial but scheming junior stockbroker - has been found out as telling porkies. He untruthfully claimed that he had a wife who had died in a car accident, a lie which has led the Sun newspaper to launch a "Kick Out Nick" campaign.

The show has taken a further credibility blow this week by the disclosure that the "live" 24-hour stream supposedly available to viewers on the internet is, in fact, heavily edited. Moreover, the programme website has been crashing with increased regularity, due partly to the massive interest and partly because the site cannot be properly accessed with an ordinary computer and phone connection.

For all that, the show has provided some quirky attractions. While intelligent conversation might be thin on the ground and discussion of politics and current affairs non-existent, the interaction, bonding and friendship-building between the cast can be entertaining, and even uplifting when one considers the quite different backgrounds the contestants are coming from.

Consider, for instance, the sight this week of laddish Nick taking Thomas under his wing, and then coming close to tears when the soft-spoken Catholic got nominated for eviction. The two had developed a strange sort of brotherly routine, following each other around the house, Nick in his England football jersey and Thomas in his bright green GAA top.

Whether you loathe it or love it, the Big Brother concept looks like it is here to stay. An Irish version is due to start next month on the student-oriented Oxygen website. Up to 400 budding exhibitionists have applied for the chance of being placed under surveillance for a year in a flat in Dublin.

But any hopefuls looking to make it big by baring all on camera should remember showbiz is a fickle business, as Anna may yet find out. One tabloid this week branded her "sneaky" for nominating Thomas for eviction and claimed she was "the prime mover in the plot to turf out" the popular Ulsterman. Any more negative publicity like that and Anna's 15 minutes of fame may be over before the eight weeks are up.

jhumphreys@irish-times.ie

Links: www.bigbrother.terra.com; www.oxygen.ie