David Willetts might have now been in the shadow Cabinet, with a full Government department to cover. But his resignation as Paymaster General for “dissembling” during a Select Committee inquiry into the cash-for-questions scandal left questions over his head. So he is deputy to two masters: Stephen Dorrell, for whom he will be covering employment, and Peter Lilley, the shadow chancellor, whom he is assisting in his complete rethink of Conservative policy. But they are both important roles, giving him opportunity to comment on Labour’s central Welfare to Work scheme and a key role shaping the future party direction.

Mr Willetts, clever and articulate, has been a senior Conservative party thinker for years, although he is only 41. A teachers’ son, he sailed through King Edward’s, Birmingham, and got a first in politics, philosophy and economics at Christ Church, Oxford, before joining the Treasury, intellectual powerhouse of the civil service. At the Prime Minister’s policy unit in the mid 1980s, he became a Thatcherite devotee and, in 1987, left the civil service to become director of the Centre for Policy Studies, the right-wing think tank.

He was adopted as candidate for the Hampshire seat of Havant in 1990, amid stiff local competition, and won the seat in 1992. Initial resentment faded when Mr Willetts turned into a hard-working, efficient constituency MP. “We didn’t want to like him but he is very charming,” a local observer said.

Once in Parliament, he rose quickly, becoming parliamentary private secretary to Sir Norman Fowler, party chairman, a Whip and then a Treasury minister.

Sheila Lawlor, Mr Willetts’ former colleague from the CPS, says: “One of his great strengths is his mastery of the technical detail of every policy aspect - from the finance to the implementation - and his ability to relate tiny details to the broad sweep.”

His ability, combined with ferocious ambition and a certain lack of sensitivity, may explain the “dissembling” debacle and some colleagues coolness towards him.

Once closely allied with Mrs Thatcher’s brand of free-market liberalism, he supported Peter Lilley in the leadership campaign. But he has repositioned himself, urging the construction of a “civic Conservatism” which can foster the public good.

He is married to Sarah Butterfield, a successful artist, and they have two small children.