By BBC Media Correspondent Nick Higham

Sir John Birt, it is sometimes said, is the man who saved the BBC. He reformed its journalism, introduced an internal market and slashed waste, in the process seeing off the threat from Margaret Thatcher's Conservative government, which would have privatised the Corporation, or worse.

He went on to embrace the digital age, positioning the BBC at the technological cutting edge, launching new channels and new services (like BBC Online) and ensuring that as audiences gradually migrated to the multichannel interactive world the BBC went with them.

Remote

Others disagree. To them he was a remote figure who cared more about structures and cost-savings than about programmes, whose reforms neutered BBC news and current affairs.

Commercial rivals saw Birt's BBC as a ruthless, publicly-subsidised competitor with apparently limitless ambitions: an unfair competitor unshackled by regulation.

John Birt joined the BBC from London Weekend Television in 1987 as deputy director-general. The BBC had aroused hostility from Mrs Thatcher's government, which detected a left-wing bias in the news and was angered by programmes like Real Lives (which included an extensive interview with Martin McGuinness, then said to be a leading IRA man) and a Panorama which alleged links between some Tory MPs and far-right groups.

Analytical journalism

At the BBC John Birt put his theory into practice, insisting on more analytical journalism, recruiting more correspondents with specialist knowledge and launching several new TV current affairs strands.

But to some the result was to make programmes less challenging, and many long-serving BBC journalists were furious.

To drive down costs in the BBC he introduced an internal market, to give programme-makers the option of using BBC resources like studios and camera crews or buying in from outside.

The reform saved millions of pounds, which became available to invest in new programmes and new services. But the system was blamed for job losses, for the loss of craft skills, and for being inflexible and bureaucratic.

Attacks

A succession of high-profile attacks were launched. In 1992 Michael Grade, the chief executive of Channel 4, described the Birt management style as 'pseudo-Leninist' and claimed it was damaging staff morale.

A year later the playwright Dennis Potter famously called Birt a 'croak-voiced Dalek'.

By now John Birt was director-general and engulfed in controversy of a different kind, when it emerged that he hadn't been on the BBC's staff but had been paid through a private company. At one stage it was thought the BBC's governors might force him to resign.

Job losses

Birt went on with his programme of change - securing a new Royal Charter for the BBC and an extension of the television licence fee.

A manifesto entitled Extending Choice argued the BBC should move towards the higher ground, developing services of distinction and quality rather than seeking large audiences. At Radio 1 the policy resulted in a much more 'distinctive' service, different from commercial pop stations - but one whose audiences went into free fall.

While many BBC programmes - Pride and Prejudice, The Human Body, Walking with Dinosaurs - were praised for their high quality, there were criticisms, not least from the BBC's own governors.

The BBC proved unable to hang on to sports rights in competition with ITV, Channel 4 and the immensely wealthy BSkyB. And the daytime programme Vanessa was shown to have broadcast interviews with fake guests - evidence, said critics, that competitive pressures were forcing the BBC to cut corners and embrace sensationalism.

As the digital broadcasting era dawned John Birt decided that the BBC had to use the new technology to find new ways to reach listeners and viewers, if it weren't to see its audiences dwindling.

Internet site

So the BBC now runs one of Europe's most popular internet sites. It's involved in half a dozen pay-television channels. And there are free, public service channels like BBC News 24 and BBC Knowledge. It awaits a decision from the government on proposals for an increase in the licence fee to pay for expansion - or a special supplementary licence paid only by those with digital receivers.

It will fall to Greg Dyke to resolve some of the unanswered questions which even Sir John's famously rigorous approach to problem-solving could not despatch.