Hillary: the other woman in the life of the President

Now Mrs Clinton is Secretary of State: the First Diplomat: a role arrived at after she unsuccessfully bid for vice- president. She must forge one of the most important relationships in American government with the man who beat her to the job she so fervently believed she deserved.

Since the election victory, the duo have been at pains to show a unified front - Barack embraces Hillary at every public opportunity, she responds with that look of fixed, over-joyous astonishment.

But doubts remain about how such a historically complicated relationship can thrive without tension.

As New York Times columnist Maureen Dowd put it: "With the Clintons, you don't get two for the price of one. You get two for the price of two."

The vastly wealthy Clinton Foundation's eagerness to attract foreign money has already caused criticism. A Secretary of State must be above suspicion when it comes to accusations of influence-peddling.

That means her husband must accept more restrictions on his globe-trotting, plutocratic lifestyle than he might like: or risk damaging her.

Physically, she is in good shape for a woman of 61, despite a gruelling schedule since leaving the White House and an aversion to all exercise except walking.

She earned cross-party admiration for her efficiency as a New York senator. Her style has moved on from the "sisterhood of the travelling pants suit" - but is still formal compared with the stylish Obamas. Her daughter Chelsea is now more often her consort at major events than her husband - the two women are a political as well as a family unit.

Close friends say she has just about accepted that her bid for the top job is over. Some of her key staff have moved across to Obama's coterie.

Yet her team still spools forth emails from Bill, Chelsea et al praising the brilliant achievements of Mrs C - as if nobody had pressed the "stop" button after she lost.

This weekend, it was her mother Dorothy's turn to preach the "I'm so proud of Hillary" gospel.

She's also a pragmatist, aware of the need to make a success of the role of Secretary of State: both because America's damaged standing in the world needs to be repaired and a series of crises loom from Gaza to nuclear Iran and unstable Pakistan.

One of her first demands was direct access to the President at all times. Not for nothing did she inhabit the White House for eight years and learn that, when it comes to the presidency, unfiltered access is everything. She has also won the argument on cutting across the State Department's hierarchies by appointing trusted envoys to oversee policy in key areas - a practice introduced by her husband.

So Richard Holbrooke takes on the most difficult US entanglement in Afghanistan/Pakistan, Denis Ross takes on Iran. There is to be no danger of repeating the Bush era shift of power over big decisions away from the Secretary of State's fiefdom to any other part of the bureaucracy.

Politically, Mrs Clinton is a bold chiaroscuro of strengths and weaknesses. She can be harsh, false-sounding, inflexible, brassy and humourless. But she has a lawyer's talent for assimilating knowledge very similar to Mr Obama's.

Her famous campaign advert "It's three in the morning in the White House..." - highlighting Mr Obama's lack of experience in the event of a sudden crisis - failed to persuade.

When the phone goes at three in the morning from tomorrow, it will be received by the first African-American President, not the first female one.

'Lady Macbeth' turns to diplomacy

Age: 61

Childhood: Brought up in middle-class Park Ridge, Illinois. Mother Dorothy was a Sunday school teacher, father Hugh a businessman. Has two brothers, Hugh, 58, a lawyer once caught up in a presidential pardons scandal, and Tony, 54, a consultant.

Education: Studied political science at Wellesley College, a women-only university in Massachusetts, then Yale Law School.

Career: Worked in Congress on Richard Nixon's impeachment, law lecturer in Arkansas then partner in Rose Law firm from 1978 until 1994.

Family: Married Bill Clinton in 1975. Only child Chelsea, 28, works for hedge fund.

Style: Once known for frumpy dresses and thick glasses, she has transformed herself into a smart Washington operator.

Good times: Being named Secretary of State by Barack Obama. Now the world's most powerful diplomat.

Bad times: Hate figure for Right; Lady Macbeth reputation; botched healthcare plan; husband's adultery; being part of a sleaze-tainted administration and running a campaign for the Democratic nomination which failed to engage the voters.