Margaret Beckett: Pack it in! Leave it alone!

With these words, the Foreign Secretary revealed the strains of her new job. Can she regain her composure?

"Ah, Margaret," sighed one of Tony Blair's most trusted advisers. "She's our Claude Makelele." Margaret Beckett, with her equine features and regal bearing, is more usually compared with the Princess Royal than Chelsea's holding midfielder, but will no doubt appreciate the compliment.

Breaking up attacks and slowing the passage of play before neatly passing to a colleague, it is not for nothing that Downing Street made her "minister for the Today programme". Only suddenly it's all going very wrong. Her tone - formerly even, rational and precise - has lately become hectoring, aggressive and rattled.

Forced to defend what most of her colleagues believe is the indefensible failure to call for an immediate ceasefire in Lebanon, Beckett has repeatedly lost her temper in the past fortnight. "Pack it in!" she snapped at Ed Stourton on Monday, having earlier picked a fight with his Today colleague Jim Naughtie. "Oh for goodness' sake, Adam, leave it alone," she barked at Sky's political editor, Adam Boulton, last weekend.

Worse, her own officials are briefing against her, talking from behind their hands about her lack of Middle East knowledge. Laced with the sort of snobbery only high-bred Foreign Office mandarins can summon, one comment was: "Frankly, there certainly was a need for a little homework." Of all the many unpleasant things that have been written about the new Foreign Secretary in the past two weeks, that remark, in particular, will have cut to the quick.

Raised by her mother, an infant school teacher (her carpenter father was disabled when she was three and died nine years later), the young Margaret prided herself on her attention to detail. She has nursed a reputation for hard work and loyalty through a long career in the Commons that began an astonishing 32 years ago.

The man she first beat was Dick Taverne, who had defected from Labour a generation before the creation of the Social Democratic Party in 1981. At the time Beckett was firmly of the left - her politics rooted in her own humble beginnings as well as in strong feminist and pacifist convictions.

A member of the Campaign Group, she opposed the expulsion of Derek Hatton and the rest of Militant Tendency and the memories of the Beckett of those days lingers among other working-class ministers who claim to have always supported what became New Labour.

A friend said she made two big decisions when she entered the Commons aged 31. The first was never to court media attention; the second not to have children. "She just thought in those days that it was impossible to combine being a mother with being in politics."

It was a typically tough-minded choice, one Condoleezza Rice, the US Secretary of State, who has also devoted her life to public service might particularly respect. But unlike Condi, Beckett is married. She met Leo, an ex-fitter with two sons and a failing marriage, during that 1982 fight for the Lincoln seat (she later switched to Derby South).

They are one of Westminster's most enduring couples. He is 15 years older but one could not describe Leo as a senior partner. To some the pair seem incongruous, ill-suited almost. Where he is easy-going, gregarious and sometimes emotional, she is reserved, forensic and is capable of chilling a room in seconds.

Almost as hurtful as the accusation of ignorance will have been the irritation her officials expressed about the presence of Leo "hanging around" her office. A friend says: "They come as a package - that's what people need to understand. In every job she's had her private office and they have had to get used to having Leo there, chattering away. It can be irritating in a busy office, but Leo gives her tremendous support and people have to understand that."

It is, of course, with Leo that Beckett takes her now famous caravan holidays to France. This fixture of the silly season for over a decade, and until this year reported with a measure of affection, is now an excuse for a renewed assault on her credibility. She was unwise, perhaps, to say she thinks caravanning "cool", but it is surely not her fault that she now trails not just a mobile home but a detail of close protection officers as she takes to the open road.

Her refusal to adopt more modish travelling is of a piece with her loyalty to those out of political favour. "She never drops people, no matter how unfashionable they have become. She kept all her old friends on the Left come what may," says one.

She even remains on reasonable terms with John Prescott, with whom she had a turf war. The Becketts and Prescotts were prickly neighbours when both lived in Admiralty House, the grace-and-favour flats off Whitehall. Margaret and Leo disliked the Deputy PM's habit of playing loud jazz late into the night.

Her quantities of unflashy loyalty and hard work bought her first the admiration of first John Smith, who said she was "proof that the rehabilitation of offenders works", then Mr Blair.

In 1994, when she was Labour leader for the period immediately after Smith's death, there was an attempt to warn her off standing for the post against the young star. Her refusal to be bullied out of the race had consequences and, although given the trade and industry brief by Blair in 1997, looked like being an early reshuffle casualty.

Indeed pundits have confidently lined her up for the chop every time the jungle drums from Downing Street have sounded an approaching Cabinet shake-up. What they failed to appreciate was that Beckett and Blair, while divided by old partisan affiliations, share similar political instincts. Both are cautious pragmatists with an instinctive feel for Middle England. She wavered on Iraq but, once persuaded, set about helping deliver a reluctant party with her usual tenacity.

She has been loyal and competent. He has rewarded her by first sparing her from the sack and then elevating her into one of the four great offices of state.

"Fuck!" she said when she found out Blair had made her Foreign Secretary in May. She swears a lot, according to former colleagues. "Vividly and with great dignity," says one. "She avoids the 'c' word generally but would never say as weak a word as 'bloody'."

The air in King Charles Street, home of the Foreign Office, must now be richly blue. Friends have little doubt Beckett is as appalled by Israel's military tactics as any other cabinet minister. She will not say so - even to those she trusts - but her inner conflict is all too obvious from her raw outbursts of anger when cornered, they say. Yet those that know her best say she will master herself and her brief in the way she has always done. The snobs at the Foreign Office will get used to her caution, her preference for the low-profile effective initiative over spin. They might even get used to Leo.