When the Savile scandal broke, he had portrayed himself as a hands-off chief executive who relies on a BBC system under which issues are brought to his attention by competent editors and executives.

He pleaded the same in a combative BBC radio interview on Saturday, saying that the McAlpine report, as far as he could tell, had been referred to senior figures in the BBC's news, management and legal divisions.

Marsh, the former BBC editor, said Entwistle's position became untenable after those comments and appearances made clear the executive had no idea what was going on within his own organization.

"This was an absolutely catastrophic combination of events," he said. "He inherited a massive crisis over Jimmy Savile. He made some missteps in managing that. He then never corrected those missteps and that helped generate the Lord McAlpine crisis."

The BBC Trust's chairman, Chris Patten, called Saturday "one of the saddest evenings of my public life" but praised Entwistle's "honor and courage" in tendering his resignation.

"At the heart of the BBC is its role as a trusted global news organization, and as the editor-in-chief of this organization, George has very honorably offered us his resignation because of the unacceptable mistakes and the unacceptable shoddy journalism which has caused so much controversy," Patten said.

British Culture Secretary Maria Miller welcomed the resignation, calling it "regrettable but the right decision."

"It is vital that credibility and public trust in this important national institution is restored. It is now crucial that the BBC puts the systems in place to ensure it can make first-class news and current affairs programs," she said.

Media watchers say doing so could mean rethinking the management structure of the BBC, whose portfolio of radio and television channels dominate the British media landscape.

"The BBC has been run by too many people who are insiders and there's no clear chain of command," said Charlie Beckett, director of the London School of Economics think tank Polis. "It has such a strong, closed-system culture that it needs an injection of fresh thinking."

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