Tom Kelly - one of the prime minister's two official spokesmen - is highly respected and has been dubbed a safe pair of hands.
Kelly used to work in the Northern Ireland Office
He joined the Downing Street staff two years ago after previously working for the BBC in Belfast and London, later becoming director of communications at the Northern Ireland office.
It was Tony Blair himself who wanted Mr Kelly to get the job as his spokesman when Alastair Campbell withdrew from frontline duties.
Mr Kelly looked after the prime minister when he visited Northern Ireland at the time of the Omagh bomb because Mr Campbell was on holiday, and the pair hit it off.
Mr Kelly also impressed former Northern Ireland secretary Peter Mandelson, Mr Campbell and Jonathan Powell, Mr Blair's chief of staff, during negotiations over the peace process in Northern Ireland.
But Mr Kelly came under scrutiny in March 1998 when a document he prepared for the then Northern Ireland Secretary Mo Mowlam disclosed plans for an unprecedented PR offensive to secure a Yes vote in the referendum on the Good Friday agreement.
While ministers denied it was a plan to manipulate public opinion, Rev Ian Paisley, the Democratic Unionist Party leader, said it "makes Machiavelli look like a rank amateur".
At Downing Street, father-of-four Mr Kelly and Mr Campbell's former deputy Godric Smith regularly take the twice-daily briefings of lobby journalists.
Mr Kelly and Mr Smith are career civil servants not authorised to comment on party political matters.
Mr Kelly is expected to take a higher profile role when Mr Smith leaves Downing Street in the near future.
Mr Campbell is also rumoured to being preparing to quit as communications director after the inquiry by Lord Hutton, into the death of Dr David Kelly.
Despite his quiet manner, Mr Kelly courted controversy at Number 10, when he wrongly claimed TV reporter Kate Adie had threatened the prime minister's security by discussing details of his visit to the Middle East post 11 September.
The wrangle centred on a live interview involving the experienced reporter responding to questions from Jeremy Bowen, presenter of the BBC's Breakfast programme.
After the broadcast Downing Street made a formal complaint to Director General Greg Dyke that the information represented a security breach.
Ms Adie denied putting Mr Blair's security at risk and accused Mr Kelly, of "exacerbating the situation" by "encouraging" journalists to publish the security-sensitive information.
Last month Ms Adie accepted undisclosed libel damages from the Sun newspaper over an article that claimed she put the prime minister's life at risk.
Ms Adie, one of the BBC's best-known correspondents who retired from front-line reporting earlier this year, was not at fault.
Last December, the spotlight again fell on Mr Kelly over his briefings to journalists during the Cheriegate saga over the prime minister's wife's links with convicted fraudster Peter Foster. During that time, Downing Street appeared to struggle to get its story straight.
Mr Kelly, in his mid-40s, is currently believed to be moving house in his native Northern Ireland.