Channel 4 hails Brother hit

Caroline in the Big Brother house on Tuesday

Channel 4 has scored a ratings hit with voyeuristic TV show Big Brother - which doubled the network's normal audience on Tuesday evening.

The programme's debut attracted an average audience of 3.6 million across the hour it went out - peaking at 4.1 million and doubling the usual number of viewers between 2200 and 2300 on Channel 4.

It also pulled in a third of all 16-34 year olds who were watching TV at the time, according to the preliminary figures.

The show, imported from the Netherlands, follows the lives of 10 strangers sealed off from the outside world in a camera-filled house for two months.

Nicholas: Naked joker

One of the contestants will be voted out by viewers each week until the end of the series, when the winner receives £70,000.

Bed betting

Bookmakers are now placing odds on which contestants will sleep together first.

Victor Chandler made former sex aid seller Caroline and City stockbroker Nicholas favourites at 5-2 after a nude Nicholas leapt into her bed as a late-night joke.

However, marketing manager Andrew entered the "diary room" - in which contestants can speak to Big Brother - on Wednesday and spoke of "mounting tension" in the house.

Highlights of the contestants' antics are being shown each weekday evening on Channel 4, with 24-hour viewing available on the show's website, which crashed again as fans logged on after Tuesday's show.

US expansion

Home sweet home: The Big Brother house in east London

The US version - which started a week before its UK counterpart - is expanding, with CBS adding an extra Wednesday instalment to the schedule. It now runs six nights a week, with Sunday the only Big Brother-free day.

Early ratings have been mediocre for the series and it is being overshadowed by a similar CBS show, Survivor, which follows a group of people on a desert island.

But, like the Channel 4 version, it has been a hit with younger viewers - traditionally a hard to reach audience for CBS.

While the UK contestants are living near a gasworks, their American counterparts are staying on a Los Angeles studio lot and playing for a bigger prize, of $500,000 (£335,000).