Aged just 36, Ms Kelly, whose mother was a teacher, numbers Margaret Thatcher among her role models and has risen to the Cabinet despite giving birth to four children since she was first elected MP for Bolton West in 1997.
Tipped as a future Labour leader, Ms Kelly is an ultra-loyalist and one of the few senior Labour figures who manages to keep a foot in both the Blair and the Brown camps.
Her appointment as Education Secretary follows a short spell as minister for the Cabinet Office and three years in junior Treasury posts.
Ms Kelly came to public prominence earlier this year when she insisted the Government did nothing wrong in the fiasco that cost 750,000 Equitable Life policyholders pound;3 billion between them.
Born in Northern Ireland, she attended private schools including Millfield (fees now pound;21,000 a year) and Westminster before going to Queen's college Oxford and the London School of Economics for her masters degree. A spell on the Guardian as an economics jouralist followed before she moved to the Bank of England.
Married to Derek Gadd, she has a son and three daughters, the eldest seven, and is perhaps best known for her refusal to take ministerial red boxes home because she reserves that time for them.
She is expected to back the Blairite agenda of choice in schools. Roth's Parliamentary Profile says she "belives state schools have to be made more attractive to the middle class".
Mary Bousted, Association of Teachers and Lecturers general secretary, described her as: "A good Bolton girl who has done extremely well at the Treasury and a person we will be able to do business with."