The BBC's Roly Keating is a man with a mission. He arrived in Newcastle this week to spread the word about the Corporation's plans for expanding its digital television and radio services.

He talks enthusiastically about the launch of new channels in the new year. The words "ambitious" and "broad-based" trip off his tongue. But the big question is, not so much the content of the new services, but if anyone is interested. The phrase digital revolution has been bandied about much in recent years, but the public has been less than willing to embrace the new technology.

Keating will tell you that a third of the nation's households now have digital TV. The obvious downside of that, statistically speaking, is that the majority don't have it. And research has shown there's a hard core who claim they have no intention of getting it - ever.

This is bad news, not only for the BBC but also the Government, which has promised not to turn off the current analogue signal until most homes have digital as, clearly, depriving voters of their favourite pastime is not a good way to win votes. The date for pulling the plug has been delayed, with the analogue switch-off happening sometime between 2006 and 2010.

Broadcasters have no choice but to push ahead with plans. "We've always felt - but not had the money to act on it - that digital is going to mean something valuable to the life of the land in terms of new output and new services. We felt that, at some point, the BBC should get involved in a big way," explains Keating.

"The new services will be free to everyone ultimately. You won't have to pay a subscription for them. They should add to what we do on the established channels, not take anything away from BBC1 and BBC2."

The BBC wanted to introduce four free-to-air digital channels. Well, newish, as two would replace the current BBC Knowledge and BBC Choice. The Government said yes to three of the proposals.

BBC Four, to be launched in the spring, will be a cultural channel. There will be two new channels for children, one for the under-fives and another for the six to 13 age group. These won approval, despite fierce opposition from the commercial operators, like Nickelodeon and Disney, which resented a public service broadcaster invading their territory. Proposals for BBC Three, aimed at the 20 to 30 younger generation, were rejected as not original or distinctive enough. The BBC will submit a revised plan in coming months.

In addition, three as yet-unnamed digital radio stations were given the go-ahead. Two cover music (young, black urban and rock from the last 40 years) and a third is a speech network, drawing on archive material and with a commitment to children's radio. In addition, Radio Five Live gets an extra sports channel and the Asian network will be heard nationwide. The BBC is investing £36m in BBC Four and £40m in the children's channels. The money is coming from efficiency savings and the licence fee settlement, although the majority of extra money raised this way is going to old-fashioned analogue services as these are the only ones most licence fee payers can receive. If only the Government could pass a law forcing everyone to go digital, the situation would be cleared up in an instant.

Keating is a good ambassador, almost making you want to watch the new channels. Certainly, the children's channels will be easier to sell than BBC Four. With three young children of his own (aged eight, five and one) he has a ready-made testing panel for programmes.

These daytime channels will build on the success of hits like The Teletubbies, The Tweenies, Blue Peter, Newsround and the CBBC brand. The one for under-fives will have an interactive element with a mix of old and new characters. "It will be a lot of fun for that generation as well as being an educational resource," he says.

The "ambitious vision" for CBBC-TV channel includes an interactive magazine show every day, original documentaries and dramas. The introduction of the two channels nearly doubles the BBC's total investment in children's programming. As well as being BBC controller of digital channels, Keating doubles up as controller of arts commissioning, so his enthusiasm for BBC Four is understandable. This is, he says, "in very broad-based terms, a cultural channel, but much more than an arts channel".

Talk of cultural enrichment is more likely to deter, than attract, viewers. Although it may sound a bit arty-farty, BBC Four is targeted at anyone, no matter where they live or what their age, with an interest in arts and ideas, "and feel they want a bit more out of TV, more stimulus for the mind".

So what can we expect? Documentaries with a bias towards arts and science as well as the best documentaries from around the world. Foreign, sub-titled films will be shown alongside performance pieces. Acclaimed director Peter Brook is filming his stage production of Hamlet for BBC Four. A books programme, debate and magazine show in the style of the old Late Show are planned too. Centrepiece will be a nightly global news magazine which isn't afraid to put a country other than this one at the centre of the news.

Keating admits they might not get the mix right to begin with. For that reason he's unwilling to talk potential audience figures. It also means you can't be accused of failing to meet targets.

"It's not a ratings-driven channel. The test is whether it's proving of value, is entertaining and rewarding to the people who come to it," he says. "When we began to talk to viewers up and down the country we found a huge interest in such a series from people who felt slightly disenchanted by what they see on mainstream TV now."