Goodbye BBC Knowledge, hello BBC Four. And hello to “something satisfyingly different from the mainstream”. At least that’s how controller Roly Keating describes the content of the free-to-air digital BBC channel which starts transmitting from tomorrow, when you can also see the evening’s content on BBC2.

Early press reports - and the BBC’s own publicity - may have implied that BBC Four is an entirely new channel, but it’s really an upgrade of BBC Knowledge. Not that that’s bad news. Since its launch in 1999, Knowledge has been gathering a word-of-mouth reputation as a channel aimed at the intelligent viewer - unlike most other channels, for instance, it hasn’t been afraid to show foreign-language films and documentaries.

But its output has been, in Keating’s words, “largely dependent on the BBC archiveI It put out good programmes, but it didn’t really have that much new to shout about, and wasn’t really able to innovate”.

What’s different about BBC Four can be simply stated: more money. Its budget for its first year will be pound;35 million - about four times as much as its predecessor’s - and it will be spent on “the best in contemporary documentary, music, theatre or international cinema”, as well as news “from a global viewpoint”, and discussion programmes “on everything from philosophy to physics”. No wonder it’s being described as television for Radio 4 and Radio 3 listeners.

Who will be able to see it? According to the Broadcasters Audience Research Board (Barb), 10 million UK house-holds have multi-channel television access - via cable, satellite or digital terrestrial receivers. (Cable operator NTL says it supplies digital TV to 1.25 million homes.) In theory, all these will get the new digital channel. However, the highest viewing figure for an individual programme on BBC Knowledge has been around 100,000 - although the channel claims more than a million viewers a week.

BBC Four’s first month looks likely to entice discriminating viewers: the first week includes Peter Brook’s recent staging of Hamlet, documentaries on Goya and Henry Kissinger, music from Senegal’s Baaba Maal, and the start of a year-round books discussioin programme, Readers and Writers Roadshow. Later highlights include Bjork at the Royal Opera House, a programme about Roger Casement, and a week-long Of Apes and Men series that features novelist J M Coetzee on animal rights and a fresh look at the emotional lives of primates.

As well as new material, repeat programmes will have a place. “We’re well aware that people value great titles from the archives,” says Keating, whose credits include a stint in charge of BBC2‘s The Late Show and as executive producer of series such as A History of British Art and How Buildings Learn. “We certainly don’t want to lose the best of what BBC Knowledge has been doing, what we call catch-up programming.” He hopes the channel will be “a place that takes television’s own heritage seriously”. His team is thinking about how to mark the recent death of writer-director John McGrath, whose TV work ranged from Z Cars to The Cheviot, the Stag and the Black, Black Oil ( a Play for Today).

Given recently expressed worries about Britons’ lack of knowledge of other languages, could BBC Four help by showing more European television? “It’s something we’re extremely open to,” says Keating. “The BBC has just signed its first-ever accord with ARTE, the Franco-German cultural channel, to co-produce a variety of programmes. I suspect we will be the key beneficiary of that.”

A bright future, then - with one drawback. BBC Four will only be available from 7pm, unlike BBC Knowledge which, until last month, could be seen in the daytime. Transmission will continue until 1am or 2am.

JOHN DAVIES Free-to-air means free (no subscription fee) once you have acquired digital equipment or paid a cablesatellite operator to supply the necessary digital set-top box. More details from the Digital TV group on www.freetoview.co.uk; ITV Digital (0808 100 0101 or www.itv-digital.co.uk); Sky (08702 424242 or www.sky.com); or NTL (0800 183 1234 or www.ntl-home.com)