In a world where every Tom, Dick and Yahoo is frantically reinventing every spoke of the media wheel with every day that passes, the BBC must hold its nerve and keep its focus on what makes it unique. We must make sure that people know, without a shadow of doubt, what the BBC stands for. We must keep faith with the past, with the essential elements of our public-service tradition.

The challenge is a formidable one. But we have been here before. In the late Fifties, the BBC was on its knees. Competition from ITV ravaged the television audience. It went from 100 per cent to 28 per cent in a matter of months.

But the BBC adapted and survived. Not by mimicking ITV, but by digging deep. It reinvented popular television with shows such as That Was The Week That Was, Till Death Us Do Part, The Forsyte Saga - and connected with viewers in new ways.

The Big Idea of the BBC then, as today, wasn't only about making programmes. It was about being there for everyone. The opportunity for discovery and creativity that digital and the internet provide must be inclusive or it will be divisive. That's always been the point of the BBC - to be at the heart of national life, not on the margins.

Think of our national sense of humour; our childhood icons; our knowledge of literature or dance or cinema; our taste in food, in fashion, in garden shrubs; our understanding of other countries; our health; our environment; our language. The BBC has nourished us, moved us and amused us in all these areas.

People will want more compelling reasons to watch and listen to the BBC in the digital era. For each passion or specialist interest, whether it's science or history, popular drama or DIY, the BBC needs an iconic programme that will connect with them.

A key discovery of recent years is people's boundless curiosity, their thirst for knowledge. It has fuelled the renaissance of the BBC's factual programmes in the Nineties, from The Life of Birds to The Death of Yugoslavia, from The Human Body to last night's extraordinary film about Stalin's Russia, Gulag.

It's this thirst for knowledge that drives a stake through old assumptions about high- and lowbrow. You can play intelligently and learn entertainingly. We're learning more and more that you can't make easy presumptions about the audience.

Using new technology, we can connect with people much more enterprisingly. "Interactivity", for us, won't mean keying in a password followed by a credit-card number. It will mean having an open dialogue with our viewers, listeners and web-surfers. They will come to us for our creativity, our quality and conviction. In our information economy, that's where our common wealth lies.

Two of our biggest projects for the millennium are Simon Schama's hugely ambitious 16-part History of Britain and a vast festival, across radio and television, called Millennium Music Live. They'll be linked to the websites of schools, museums, concert venues - and to our digital channels, BBC Choice and BBC Knowledge.

I am looking forward to exploring The State of the Planet, the latest chapter in Sir David Attenborough's astonishing chronicle of natural life, with my eight-year-old son. It's nothing less than an audit of planet earth. Together, we will be able to interact with it, interrogate it and travel back through the Attenborough treasury of the past.

But there is a job to be done if we are to reconnect with those who may be losing touch with us - especially the Playstation generation of children, who are proving exceptionally fickle in multi-channel homes. They reinforce a fear that fragmentation of the audience could spell the death of public- service broadcasting as a unifying spirit in society. That a world where every programme has nine lives - or 900 million lives - will be a world without a sense of community. That the common culture which Reith's BBC helped foster will be irreparably lost.

I'm more sanguine than that. Yes, there will be fewer common reference points in broadcasting - but, in today's diverse Britain, that's not wholly unhealthy. People will want to roam more individually, and that adventure will help us define our identities better.

People will also continue to share the same events and experiences in their millions, at the same moment - whether it's the news at 9pm, a Wimbledon final, the World Cup, a cliffhanger on EastEnders or Millennium Night.

All that tallies with the experience of the internet, a domain where "trusted guides" such as BBC Online are already critical in making sense of the web. Our internet service is widely recognised as the biggest and best in Europe, particularly our news and education sites.

A vital task for us is to make the BBC itself one big trusted guide - a trusted Ordnance Survey for the digital world. No other media outlet has the incentive to provide a help-engine of that scope and public value - any more than they have the impetus to provide Newsround or The History of Britain or Comic Relief. That's what we mean, at the BBC, when we talk of a "spectrum dividend": being a beacon in an age of plenty, doing what we do best, better.