These are the darkest of days for the BBC. Weeks after the corporation was plunged into turmoil and self-recrimination over the decision to pull a Newsnight investigation into Jimmy Savile, it is paying an even bigger price for having compensated for its caution by reacting in the opposite way; rushing out another Newsnight programme on child abuse, this time accusing an unnamed "senior Tory" who we now all believe was intended to be Lord McAlpine.
In the wake of all these events it is right that the Director-General, George Entwistle, has fallen on his sword now that the flaky nature of the journalism behind this second programme shown on 2 November has been exposed, now that Lord McAlpine, unsurprisingly, is said to be suing the BBC.
Mr Entwistle was only 54 days into the job, a veritable Lady Jane Grey figure as far as directors general go. But it was unpardonable for someone surrounded by a team of well-paid communications advisers to go on the Today programme on Saturday morning and say that none of them had alerted him to the potential danger of airing such an accusatory programme – when the makers of the report about child abuse in north Wales had not contacted the chief suspect to put their accusations before him. Nor had anyone alerted Mr Entwistle to a front-page story in a newspaper effectively demolishing the story.
Mr Entwistle responded thus to his Today interviewer, John Humphrys: "The organisation is too big: there is too much journalism going on." Those telling words may well sum up much of what is going wrong at the BBC, and they should inform the work of the "radical overhaul" that Lord Patten promised yesterday.
At the same time, Mr Entwistle should have realised long ago that the Savile case was growing octopus-like tentacles, each one of which needed the utmost scrutiny. As it is, his baffled, complacent-sounding defence was an absolute gift thrown in the direction of the BBC's enemies. They are legion on the right, and have been thirsting for years to see the corporation well and truly skewered for what they are convinced is its pro-European, anti-Tory, and generally soft, soggy-left, bias.
The danger now is that of a kind of witch-hunt gathers pace, each resignation fuelling suspicion that someone else less deserving has been allowed to remain at his or her post, thus feeding the clamour for more victims.
Those of us who treasure the BBC need to be fully aware of the less than pure motives of some of those who are loudest in demanding that heads roll fast and in large quantities. The BBC is not, in fact, a modern-day Augean stable that needs cleaning out from top to toe. Mr Entwistle's true failing, as MPs recently pointed out, was his incuriosity, a lamentable failing in this case, but not the most cardinal of sins.
We also need to bear in mind that the Director-General was not forced out by some external force, but after being placed under the equivalent of a microscope by one of his very own journalists. That in itself is a reminder that the culture of the corporation is anything but rotten and self-serving. The zeal of BBC journalists in reporting the BBC's own blunders over the Savile case has been something to behold; it's hard to imagine any other organisation of that size in this country, or elsewhere, being so relentlessly self-critical.
It may well be that others in the former Director-General's entourage, especially those running the slumbering communications department, will have to consider their positions. What the corporation does not need in the difficult months ahead is to become entirely rudderless, a plaything of its enemies.
Rather than delivering up one sacrificial victim after another, the overhaul that Lord Patten has promised needs to concentrate on the systemic flaws besetting a behemoth such as the BBC has undoubtedly become. A clearer line of demarcation needs to be drawn in future between the responsibilities of the chief executive and the head of news, so that the former is not obliged to assume immediate ownership of the factual accuracy of every story that is produced.
When it comes to choosing a new director-general, it is time for the BBC Trust to consider an outsider over another "safe pair of hands". In terms of "culture", admittedly a vague concept, the BBC needs to become both more confident and at the same less careless and reactive.
Just after the BBC's 90th birthday celebrations in September, an event that took us back to the days of the first Director-General, Lord Reith, a good hard look at the principles that guided that stern but assured BBC boss might be a start.
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