George Entwistle, the director general of the BBC, last night resigned from his £450,00-a-year post, leaving behind a broadcasting institution in crisis.
His departure was triggered by a Newsnight documentary that wrongly implicated UK politician Lord McAlpine in a child sex-abuse scandal, just weeks after Newsnight failed to broadcast an investigation into the alleged child abuse of the late BBC star Jimmy Savile.
In a brief statement outside BBC headquarters in London, Mr Entwistle said that he had decided to do the "honourable thing" and step down.
"When appointed to the role, with 23 years' experience as a producer and leader at the BBC, I was confident the trustees had chosen the best candidate for the post, and the right person to tackle the challenges and opportunities ahead," he said.
"However, the wholly exceptional events of the past few weeks have led me to conclude that the BBC should appoint a new leader."
Questioned by John Humphrys on the Today programme, he disclosed the full extent of his ignorance of the broadcast and said that he had not read any papers last Friday morning, which disclosed that Lord McAlpine was innocent, as he was delivering a speech.
Asked by Mr Humphrys: "You didn't know that that actually happened?" Mr Entwistle replied: "No, I'm afraid I didn't."
Last night Newsnight star presenter Jeremy Paxman issued a statement, saying: "George Entwistle's departure is a great shame."
Caroline Thomson, the BBC's former chief operating officer, is said to be favourite to become the new DG.