Alastair Campbell has given notice that he is to leave his post as Tony Blair's communications chief just days after giving evidence to the Hutton inquiry.
The inquiry has heard a host of evidence shedding light on the key role Mr Campbell has played at the heart of Tony Blair's government.
He not only chaired meetings in the run-up to the publication of the controversial Iraq weapons dossier, but was also involved as Downing Street and the Ministry of Defence debated how to proceed once Dr David Kelly came forward to admit to speaking to BBC reporter Andrew Gilligan.
Whatever the final outcome of the Hutton inquiry, few will challenge the suggestion that historians will judge Mr Campbell's wide-ranging role as his master's voice to have been as significant - if not more so - than that performed by Sir Bernard Ingham for Margaret Thatcher.
A bullish Campbell on Channel 4
Indeed, while Sir Bernard's words were regarded by political journalists as the authentic echo of his boss, some suggest that with Mr Campbell it is sometimes the other way round: that when the prime minister speaks, what you get is pure Campbell.
And for all his closeness to Margaret Thatcher, Sir Bernard was never regarded as "the real deputy prime minister".
Mr Campbell's appointment was unlike any before him: a political appointment to a civil service post, with civil service rules changed to allow him to express political views.
This led to opponents arguing that this meant the taxpayer was forking out for a party political propagandist.
He also changed the way Downing Street press chiefs are seen in the outside world - he has become a public figure in his own right.
Mr Campbell moved to Downing Street alongside Tony Blair in 1997 having worked for the Labour leader in the same role in opposition.
After the last election, he handed over the role of prime minister's official spokesman (PMOS) to take on a more behind-the-scenes role.
But his profile within the government didn't slip in the slightest. Quite the opposite in fact, as the Iraq dossier row developed over the summer.
Mr Campbell is a former political journalist and a loyal Labour supporter, though neither characteristic marks him out as particularly unusual in terms of previous prime ministerial press secretaries.
Francis Williams, for instance, had worked for the Daily Herald before becoming a civil servant and then Attlee's press secretary.
Sir Bernard: Highly valued by Margaret Thatcher
Trevor Lloyd-Hughes, press secretary to Harold Wilson, came straight to the job from the Liverpool Daily Post, and he was followed by Joe Haines, an experienced lobby journalist. Like Mr Campbell, Mr Haines had Labour credentials.
Many press secretaries have been journalists who subsequently turned to the civil service, including Sir Bernard Ingham, who had previously worked for Tony Benn when he was a Labour minister.
Other press secretaries, such as the three who served John Major - Gus O'Donnell, Christopher Meyer and Jonathan Haslam - have been career civil servants.
All were seen as close to Mr Major, with Mr O'Donnell in particular seen as reflecting the character of his boss and is credited by some as playing a part in Mr Major's "nice guy" image.
Mr Meyer - now Sir Christopher - was seen as more flamboyant, revelling in his spats with the press before heading off to become the British ambassador in Washington. He now heads the Press Complaints Commission.
Perhaps the most famous prime ministerial press secretary, however - at least until the arrival of Mr Campbell - was Sir Bernard Ingham.
His relationship with journalists was sometimes stormy - and there were occasionally questions about whether his briefings blurred the lines between the business of government and politics - but he was well regarded by the lobby.
More importantly he was highly valued by the prime minister.
Indeed, most press secretaries seem to have remained on good terms with their prime ministers, Mr Campbell included.
Mr Campbell was closer to his boss than any press chief before him. His loss will be keenly felt by the prime minister.