So just who led the BBC into its darkest hour? Take a look at the prime suspects

In a wood-panelled room in the prow of the old Broadcasting House, the director generals met for dinner. They were nearly all there - stretching back decades, up to Tim Davie, then the current DG, who had invited them all to join him.

- writes Ceri Thomas

According to one of the men who attended, it was an unlikely evening. By his account, it went like this: John Birt had prepared a few words, an unvarnished description of the domineering John Reith, the founding father of the BBC. The DGs stood and toasted Reith. Davie, too, made a toast, a knowing one: “To all of us, for surviving.” Greg Dyke, who was forced out over the BBC’s Iraq war coverage, joked: “You haven't, yet.” And he didn’t. Roughly a year later, Davie, too, was out.

There is a mystery behind the resignations of the BBC's director general, Tim Davie, and the chief executive of its news division, Deborah Turness. The puzzle is not that there were resignations - there have been five BBC DGs this century and three have been forced out early - but the scale of the problem that caused them. Because the bad edit of Donald Trump's speech on Panorama was a serious one, yes. But it was not an argument about whether the country was lied to before it sent soldiers to fight and die in Iraq, which led to Greg Dyke’s downfall in 2004. Nor was it about the role the BBC may have played in enabling Jimmy Savile to hide in plain sight while he abused hundreds of children; the scandal which brought down George Entwistle in 2012. Those events sit in a different category from the Trump edit, and they leave the BBC to ponder a troubling question: what has changed? It used to take an explosion - something felt across the whole country - to unseat a DG. Can you do it now with a peashooter if you blow it often enough?

Why was nobody sacked?