after the BBC was castigated by a public inquiry over a report alleging government impropriety in the fevered build-up to the war in Iraq, leading to major organisational changes.
One of the BBC's most prominent figures, Newsnight presenter Jeremy Paxman, said that since the Iraq report furore, management had become bloated while cash had been cut from programme budgets.
He (Entwistle) has been brought low by cowards and incompetents, Paxman said in a statement, echoing a widely held view that Entwistle was a good man who had been let down by his senior staff.
Cameron appeared ready to give the BBC the benefit of the doubt, believing that one of the great institutions of this country could reform and deal with its failings, according to sources in his office.
Patten, who must find a new director general to sort out the mess, agreed that management structures had proved inadequate.
Apparently decisions about the programme went up through every damned layer of BBC management, bureaucracy, legal checks - and still emerged, he said.
One of the jokes I made, and actually it wasn't all that funny, when I came to the BBC ... was that there were more senior leaders in the BBC than there were in the Chinese Communist Party.
Patten ruled out resigning himself but other senior jobs are expected to be on the line, while BBC supporters fear investigative journalism will be scaled back. Patten said he expected to name Entwistle's successor in weeks, not months.
Among the immediate challenges are threats of litigation.
McAlpine, a close ally of former Prime Minister Margaret Thatcher, has indicated he will sue for damages.
Claims for compensation are also likely from victims who say Savile, one of the most recognisable personalities on British television in the 1960s, 70s and 80s, sexually abused them as children, sometimes on BBC premises.
Two inquiries are already under way, looking at failures at Newsnight and allegations relating to Savile, both of which could make uncomfortable reading for senior figures.
Police have also launched a major inquiry into Savile's crimes and victims' allegations of a high-profile paedophile ring. Detectives said they had arrested their third suspect on Sunday, a man in his 70s from Cambridgeshire in central England.
Funded by an annual licence fee levied on all TV viewers, the BBC has long been resented by its commercial rivals, who argue it has an unfair advantage and distorts the market.
Murdoch's Sun tabloid gleefully reported Entwistle's departure with the