Britons have been warned by no less an authority than India's new Prime Minister Morarji Desai that when a woman in politics turns devilish she beats all records.

"Thatcher will be the same if she becomes prime minister of Britain, let me tell you that," said the 81-year-old celibate whose attitude toward women in politics has perhaps been blighted by another very political lady.

In fact, if there were a general election in Britain tomorrow, polls unanimously predict, the British electorate would take the risk, and the leader of her majesty's loyal opposition, Margaret Hilda Thatcher, would become Britain's first woman prime minister. In the year of Queen Elizabeth II's silver jubilee, a grocer's daughter from Lincolnshire would be summoned to Buckingham palace, and, in the footsteps of Disraeli, Churchill and MacMillan, be asked to form a Conservative government.

While the Labor government struggles on in the House of Commons with the uncertain support of 13 Liberal members of Parliament, Thatcher is keeping her calender free in the autumn for the general election she says is inevitable this year.

Meanwhile, the voters are in a vengeful mood over inflation running at 16 per cent a year and with more than 1.3 million Britons unemployed. Laborite Roy Jenkins' old seat at Stechford fell to the Conservatives with a swing of nearly 18 per cent in the latest test.

Early Friday, Thatcher's Conservatives captured the rock solid Labor seat of Ashfield, a mining constituency. Labor did, however, manage to hold on to the seat at Grimsby of the late Foreign Secretary Anthony Crosland.

As a result, Labor's majority in Commons is one less and the government is even more dependent on Liberal support for survival. This will probably hold up. The Liberals were trounced at both by-elections and are unlikely to want a general election yet.

Although some observers say the prospect of power has turned Thatcher on, and a new purposeful hairdo has replaced her previous-impeccable coiffure, many questions remain about her tactical judgment, her political beliefs and her personal style.

As a trained tax lawyer and chemist who perhaps uses statistics with greater sensitivity than words, Thatcher did well in her recent reply to Chancellor of the Exchequer Denis Healey's budget speech.

But that performance only partially repaired a parliamentary reputation severely denied by her attempt to bring down the government with a motion of no-confidence argued in a speech generally rated as one of the worst of her career.

It was left to the parliamentary correspondent of the Times, Hugh Noyes, to put the front-page knife in:

The best advice that Thatcher's advisers could give her after her performance, he said, is that she should lie low for some considerable time, dismiss all her speech writers and move no further no-confidence motions.

"Her timing was badly out, her quotations were poorly selected and her jokes fell flat," he said.

She apparently had taken only 20 minutes with her shadow cabinet to decide to risk all. But before long she was seen in the House of Commons tearooms asking Tory members if she had done the right thing.

Some sympathetic observers have grave doubts now over the consequences of that decision.

What Thatcher did was to force the Labor government into the arms of the Liberals, making the government look less socialist and leaving an aura of moderation should the economy really turn round in the next two years and the Liberal-Labor liaison survive. The Tory leader also forced the humiliation of her greatest electoral asset - Labor's truculent left wing.

"The Tories," spluttered Tory editor Peregrine Worsthorne in the Sunday Telegraph, "have shot their own fox."

With an even longer perspective, Ronald Butt, writing in the Sunday Times, said the great danger for the Conservatives was that the Liberals would become absorbed in a new kind of "broad left" that could dominate British politics for the next decade and beyond.

Another worry for Thatcher is the unpleasant things people, particularly journalists, say about her. It may be a litany of images of coldness and competence intoned by men about a woman about to make it. But if people say she has "cold determination, analytic strength, superhuman tolerance to tedium, brutal honesty" and label her variously as "iron maiden, stainless-steel Dresden doll, the Pasionaria of middle-class privilege, Maggie-one-note or Edward Heath-in-drag," it does not really matter whether the descriptions are fair or true - if enough people believe them.

At least one Saudi prince has a soft spot for her. After a meeting between her and Crown Prince Fahd, one of the royal poets was instructed to write extolling her virtues. The poem read:

"My heart raced when I saw her face to face.

"Her skin as smooth as ivory

"Her cheeks as rosy as an English rose

"Her eyes as lovely as a mare

"Her figure is more attractive than the figure of any cherished wife or coveted concubine."

If the electoral tide is running against the Labor government, no defects in Thatcher as a politican, real or imagined, would stop Britain having a woman prime minister.

Britain votes predominantly along party lines and disillusioned Labor voters who dislike Thatcher's politics are more than capable of easing her progress to power by staying at home on election day.

But Thatcher does have image problems though a Conservative official says, "she is a superb communicator face to face, in Parliament and on the political platform" and will only admit that she finds it a little difficult to relax on television.

In fact, Thatcher has had the services of television producer Gordon Reece for the past two years to try to improve her act. Many people are put off by her slow, deliberate, sledgehammer delivery and a voice pitch that becomes shrill when excited.

Reece will not discuss his advice to the Tory leader but journalists noticed her voice became less shrill, and certainly during the past two years she has changed to a more flattering hair style, clothes that emphasize a new slimmed-down figure and a more skillful use of makeup.

But television remains a problem. Recently faced with four woman television interviewers, she said, "yes," she knows her voice goes squeaky when she is nervous. She writes "slow-relax" in big letters at the top of her speeches.

"I've got used to criticism about my voice," said Thatcher. "I know it goes high when I'm apprehensive and nervous and I can hear it."

To a suggestion that she had changed her voice and accent over the years to be more "posh," she replied: "No. I've tried to get my voice down lower." She also vehemently denied ever having elocution lessons, although this has been reported many times - quoting people who were at speech school with her.

The Tory leader attributes her porcelain vowels and the clarity of her diction to the poetry reciting competitions she used to enter and win as a schoolgirl.

The recent voice change was also noticed by the finely tuned ear of Janet Brown, the woman who makes a living impersonating Thatcher on television. The voice used to sound like a wound-down record, everything slow and measured, she said. "Now she's much sharper, with more blanks between words. What's fascinating is that they're always silent blanks. I've never heard Margaret Thatcher 'um' or 'er' - never once - which is unbelievable when you think of it."

Yet some Tories are wondering if the attempt to alter her presentation might have been counterproductive - increasing tension rather than reducing it.

Maurice Trowbridge, Conservative Party deputy director of publicity, said: "People are wondering whether his [Reece's] influence over her for the past two years was entirely beneficial.It is being suggested that in trying to produce the attributes necessary for television there was a tendency to lose the person.

"Gordon Reece tried to teach her everything as he saw it. There was criticism of the pitch of her voice. He was successful in modifying the pitch - making it less shrill. Perhaps a little too much. Sometimes she sounded almost sultry," said Trowbridge.

The skillful modulation of the voice does not really prevent the personality of a lifetime showing through. There has not been much room for frivolity in the serious life of Margaret Thatcher. At school, her friends say she was always tidy, good at everything from academic subjects to sports, and never went to a dance until she was at Oxford University.

Her politics are also serious. She seems to personify the work ethic. The book she says has influenced her most profoundly is by an American Anglophile: "A Time for Greatness" by Herbert Agar published in 1943 - a hymn to the virtues of self improvement and will power which opens witha chapter on the "Sickness of the West" and warns that the democratic tradition must be renewed and served more faithfully.

Domestically she has appeared to be an uncompromising right-winger who supports "workers and not shirkers." Yet those who know her best say she approaches decisions carefully and tends to be more pragmatic than doctrinaire.