By Helen Bushby BBC News Online Entertainment staff

BBC Three's big moment has arrived.

Almost 18 months after its first application for a digital licence was rejected, it is now on air.

Viewers can expect "imaginative and intelligent" programming for the 25-34 age group as well as "creative risks", according to the channel's controller Stuart Murphy.

Murphy, 31, came up with fresh ideas for the channel, which is replacing BBC Choice, after Culture Secretary Tessa Jowell told him it was it was not "distinctive" enough.

We want to incubate the Risk Gene and watch it spread to other channels Controller Stuart Murphy, in a recent interview

But BBC Three will not just be under the watchful scrutiny of its rivals, such as Channel 4's digital arm E4, MTV or Sky One.

The government will review BBC Three's progress in 2004 and decide if it is fulfilling its public service remit.

Consequently, strict guidelines have been set out for the channel, which will broadcast from 7pm to 4am each day.

It must "embrace" drama, entertainment, news, current affairs, education, music, the arts and science, as well as including coverage of international issues.

And 15 hours of science, religion, ethics and business must be broadcast, plus a 15-minute peak-time news show and hourly 60-second bulletins delivering five news stories.

A typical night's viewing

7pm: Liquid News 7.30pm: Liquid (celeb) profile 7.45pm: The News Show 8pm: Blood Diamonds, a report on diamond mining 8.30pm: EastEnders 9pm: Vinnie, a reality TV show which follows Vinnie Jones 9.30pm: Dreamscapes, which explores architecture 10pm: Robbie Williams, on the making of his latest album 10.30pm: Swiss Toni, a spin-off from the Fast Show 11pm: Johnny Vaughan Tonight (above) 11.30pm Monkey Dust, a satire on urban life 12pm: Thought for Tomorrow 12.01pm: Repeats

BBC Three must also produce 90% of its shows in the UK, 80% of which should be original.

Rivals welcomed these stringent conditions, having been extremely wary of the channel poaching their viewers.

However its initial line-up will include BBC One's top-rating soap EastEnders, which will be screened a day early on BBC Three for a fortnight.

And to help raise the channel's profile, Murphy has managed to get a few well-known faces, including Charlie Higson, who will appear in the sitcom Swiss Toni - a spin-off from his comic Fast Show character.

Johnny Vaughan, who has had mixed fortunes as a presenter since leaving Channel 4's Big Breakfast, will front a chat show, while anarchic comic Dom Joly is also getting his own programme.

The channel also focuses on celebrity profiles, such as DJ Fatboy Slim, singers Tom Jones and Craig David, and, unsurprisingly, David and Victoria Beckham.

Celebdaq will be an interactive trading game, allowing viewers to trade on the value of celebrities - based on how many column inches they generate. At least 20% of the channel's output will have interactive support.

David Akinsanya is part of the current affairs strand

In Jailed by the State, journalist and former Borstal inmate David Akinsanya will trace people he met in jail to see what has happened to them.

Science programming will include an exploration of physical pleasure in Body Hits, while Dreamspaces will look at modern architecture and contemporary design, with celebrities discussing their favourite buildings.

So how does this compare with BBC Three's rivals?

E4, which receives a huge boost every time Big Brother is streamed live on it, is made up largely of repeats of highly successful shows from Channel 4 such as Friends, ER, Hollyoakes, V Graham Norton and Dawson's Creek.

Burn It: Original drama about Manchester men hitting their 30s

It also premi�res shows such as Ali McBeal and The Sopranos before they appear on Channel 4, and features the occasional new commission such as Celebrity Five Go Dating, in which models and soap stars go on dates.

TV favourites The Simpsons, Buffy the Vampire Slayer and the X-Files feature on Sky One, but it also commissions its own shows such as the football-based soap opera Dream Team.

MTV landed reality TV show The Osbournes, which broke all its viewing records with its fly-on-the-wall antics of Ozzy Osbourne's clan, while Jackass, a dangerous stunt comedy programme, was recently made into a feature film.

Ronan Keating appears in music show Re:covered

But it is more widely known for its music videos and of course its music awards.

Fraiser, Cheers, Roseanne, Ellen, Happy Days, Mash and The Cosby Show are the staple of the Paramount Comedy Channel, which also relies entirely on repeats.

BBC Three will have to break new ground in an increasingly competitive market - there is no doubt that all eyes will be on the ratings for some time to come.