THE brave volunteers who agreed to take part in Channel 4's fly-on-the-wall Big Brother show must have dreamed of finding fame.

For 24 hours a day, their every move inside the sealed house is being recorded. Excerpts are being broadcast on TV and millions more viewers are keeping an eye on them via the Internet.

This, they must have thought, could be the springboard to a whole new life as a celebrity.

But viewers have been voting to decide whether former sex aid seller Caroline from Birmingham, or London writer Sada should be evicted first.

These two women were nominated for the boot by their housemates. Every week one person will be thrown out of the house, until just three contestants in line for the £70,000 winner's prize remain.

Each contestant knew he or she ran the risk of being evicted first but Caroline, 37, and Sada, 27, were distraught to be named the least popular residents by their fellow contestants.

Humiliated on national television, they burst into tears. And for either Sada or Caroline, the misery will be complete tomorrow when she is marched out of the house.

Notoriety as the least-liked Big Brother contestant was not the kind of fame either of them had in mind.

Instead, they would have been dreaming of ending up like the winner of the first show in Holland, Bart Spring in't Veld, who has become one of his country's most famous people.

Or perhaps they might have wanted to follow the lead of the victor in the German version who now boasts his own TV show and a chauffeur-driven Mercedes.

Caroline admitted as much before she entered the house when she said: ''This will be a great experience and who knows where it will lead?''

This is not as naive as it sounds, since some participants in docu-soaps in this country have ended up as winners.

Singer Jane McDonald is a shining example. Until the TV cameramen arrived to film The Cruise she was just another struggling entertainer on a cruise ship.

Jane, who had been thinking of giving up singing all together, suddenly became the star of the show. Thanks to her new-found fame, she now has a lucrative TV job, hosting the talent-spotting show, A Star For a Night.

Another person who found fame by appearing on a docu-soap is Jeremy Spake. He wowed viewers of Airport with his jokey banter and fluent Russian to become the star of the series and ended up as a TV presenter.

Then there's Trude Mostue, who shot to fame in the BBC documentary Vets School. The Norwegian's long blonde hair and stunning looks no doubt helped her become a celebrity but the key to her success was her painful, on-air struggle to qualify as an animal doctor.

Now she is the TV vet who has become the star of two spin-off series, Vets In The Wild and Vets To The Rescue.

On an even bigger scale, multi-millionaire pop singer Sheena Easton also found success by appearing on a TV show.

Before she appeared on The Big Time, hosted by Esther Rantzen in 1979, she was an unknown club singer.

If Caroline and Sada feel they stand to lose their chance of fame, should they be the first contestant to leave the Big Brother house, it might be a consolation to know the odds were stacked against them.

When the eviction happens tomorrow, the loser will probably think her short-lived TV career is over - but the fickle public just might take her to their hearts.

l Big Brother, C4 8.30pm tomorrow

l Ray Mallon is on holiday