The BBC must never be all about ratings - or even mainly about ratings. In the past year, we have made a raft of terrific programmes which stand comparison with the best the BBC has ever done: 'Blue Planet,' 'Walking with Beasts,' 'Son of God,' 'Clocking Off,' 'The Way We Live Now,' 'Conspiracy,' 'Lost World.

I want the BBC to be a mass market public service broadcaster still funded by the licence fee... and the licence fee is more durable than many people in the commercial sector believe.

Without the BBC, the proliferation of television and radio channels by the private sector would simply result in more and more channels, with tiny audiences, all seeking to do the same thing. The future would be one of fragmentation - fragmentation without either plurality or diversity.

Over the last decade, - economists seemed to share a broad consensus about economic policy, with the old splits between monetarists and Keynesians apparently being settled by events. But the Great Recession of the last two years has changed everything.

It was an interesting question as to whether the BBC had a future in the digital world, and what form of market failure could justify the licence fee system.

There is an honourable tradition in British public life that those charged with authority at the top of an organisation should accept responsibility for what happens in that organisation. I am therefore writing to the prime minister today to tender my resignation as chairman of the BBC.

The BBC provides the commentary on our lives, the soundtrack of the nation. It is one of the most powerful unifying forces in the United Kingdom today.