Andrew Adonis is often described as a "key aide" of Tony Blair.
Mr Adonis on a visit to a school
But the term hardly begins to describe the extent of his influence and political closeness to the prime minister.
As a former head of the Downing Street policy unit, Mr Adonis was instrumental in shaping the public service reforms that are so close to the prime minister's heart.
Much of Labour's education programme - from the introduction of university tuition fees to new specialist schools (heralding the end of the "bog standard" comprehensive) and business-backed city academies have been credited - rightly or wrongly - to Mr Adonis.
He is thought to have been responsible for the final formulation of student tuition fees that was almost defeated in the Commons last year.
In fact, so closely associated is he with the Blairite vision for the future of education, some educationalists refer to government policy by the acronym ABA - the Adonis Blair Axis.
As a result of this close identification with controversial reforms, Mr Adonis has become a hate figure for some on the left of the Labour party.
He insists his detractors mistake his passion for excellence and diversity in public services for elitism.
He is the son of a Greek-Cypriot postman and a trade unionist, who went to the fee-paying Kingham School, in Oxfordshire, and then Oxford University.
A former Nuffield Fellow, he worked as a journalist on the Financial Times and the Observer, where he often wrote about the class system and the need for better public services.
He cut his political teeth with the SDP and only joined the Labour party in 1995, after Mr Blair repealed the party's commitment to public ownership.
He joined the Downing Street policy unit in 1998 and became its head in 2001 at the age of 38.
He quit the policy unit in 2003 to work full time on a biography of the late Roy Jenkins and develop education policies.