Big Brother's jackpot

Viewing figures rose when Paul and Helen got close

By BBC News Online's Ian Youngs

The winner may walk off with £70,000 and the guarantee of a week's tabloid fame - but Big Brother's importance will stretch beyond the final show.

Contestants in last year's original show sang "It's only a game show" when they wanted to pretend that they were not being watched by millions of people in what became a surprise TV smash.

The website broadcast a live video feed

Big Brother II has kept up the momentum, defying some critics' predictions that the novelty of watching 10 "normal" people locked in a house would wear off second time around.

In some ways, it has been even more popular, with the insertion of a new housemate and a budding romance keeping viewers gripped.

It has attracted just under five million viewers on average for each of its daily shows - catapulting Channel 4's share up from its usual 10% to a quarter of the total TV audience.

And that has meant big money for the channel.

Josh's introduction added extra interest

The channel can reportedly command £100,000 for each 30-second advertising spot during the show.

With two hour-long finale shows on Friday, that adds up to £1.6m in one evening alone.

Sharing the programme between new digital channel E4 and the show's website has also been hailed as a wise move - and one that will have made other TV bosses take notice.

Established

E4 was launched in January, and has claimed some of the fastest-growing viewing figures ever, thanks to up to 18 hours of live coverage from the house every day.

Some of those viewers may lose interest when the coverage stops - but E4 has now established itself in a highly competitive market.

The Big Brother website, meanwhile, suddenly became one of the most popular sites in the country after the show began, with almost 1.8 million unique visitors in May and June alone.

E4 has been screening hours of coverage a day

The site again allowed fans to watch live video of activity inside the house as well as giving up-to-date news and polls on all things Big Brother.

And adverts on the site have raised even more for programme-makers.

But the success cannot just be measured in monetary terms.

The series has kept a buzz that shows like Survivor lacked, and tabloid newspapers have been more than willing to keep that going.

More than 2,000 articles have been written about the show so far - including numerous front pages.

It is a scenario that most TV executives dream of.

But Channel 4 and Endemol say they have not decided whether there will be a Big Brother III - but it will be hard to drop such a successful format.