Dressed immaculately in an elegant floor-length gown and with her hair perfectly coiffured, the petite brunette descended the sweeping staircase to make a grand entrance to a state dinner at the White House in Washington, DC. Although she radiated confidence and refined poise, she felt a crushing self-consciousness - the result of losing a breast to cancer in a personal tragedy that had been shared with the nation. "I just knew all eyes were upon me," she said of the visiting dignitaries and heads of state who had assembled for the function. "And they were probably saying, 'Which one did they say it was?'"

Some weeks earlier, in September 1974, doctors told America's new first lady, Betty Ford, they had found a lump in her right breast. She'd been in the White House a mere seven weeks and was shocked by the discovery. She fell into "total denial". The next day, as her husband, Gerald, attended his first economic summit as the 38th President of the US, she bravely attended an official event - all charm and smiles - while keeping the devastating news to herself.

It was the same guardedness that helped her hide an addiction to alcohol and painkillers for years. A former dancer and model, Betty had grown up with the scourge of alcoholism. But while her father battled the bottle until his death, she confronted her own demons and, in doing so, reached out to help others in the grip of addiction. Today, California's Betty Ford Center - the substance-abuse treatment facility she co-founded in 1982 - is synonymous with caring for people ravaged by drugs and alcohol.

Disarmingly open and unashamedly outspoken, Betty also became a pillar of strength for women with breast cancer, and was something of a pioneer in demystifying the disease. The day the lump was found, the White House released a statement for the evening news, stating that the first lady had been admitted to hospital and would undergo surgery for breast cancer the next morning. It was an extraordinary moment in White House history - medical emergencies had previously been hidden or ignored, and in those days few people mentioned the words "breast" and "cancer" in polite society, let alone on television.

Yet the announcement was in keeping with Gerald's style of transparent presidency, which he hoped would restore public faith in the office after the resignation of disgraced President Richard Nixon amid the Watergate scandal. The nation held its breath as Betty went under the knife, but doctors discovered the worst: the lump was malignant and the 56 year old had a radical mastectomy. Stoic as ever, she shook off self-consciousness, knowing publicity over her illness paved the way for thousands of women to undergo breast checks. And she was comforted by her rock-solid marriage. "I never felt hopelessly mutilated," she noted in her 1978 autobiography, The Times Of My Life. "After all, Gerry and I had been married a good many years and our love had proved itself ... I knew he wouldn't desert me because I was unfortunate enough to have had a mastectomy."

Those who knew Elizabeth Ann Bloomer - born in Chicago on April 8, 1918 and raised in Grand Rapids, Michigan - would have recognised her signature pluckiness in those words. Her mother, Hortense, would often say young Betty had "popped out of a champagne bottle". She grew up chasing her two older brothers, often joining their ice hockey and football games, while studying ballet and attending social dancing lessons.

But Betty's sunny childhood was shattered when her father, William, a travelling salesman, died of carbon monoxide poisoning in the family garage in 1934. While his death was declared an accident, there were rumours of suicide. Betty was 16 and felt the loss deeply, but her grief was compounded when she discovered her dad had been an alcoholic. She took refuge in dance - which she'd loved from an early age - and, after graduating from high school, spent two summers studying it in Vermont. It was there that she met the influential dance choreographer Martha Graham.

Graham mentored Betty, who, aged 20, moved to New York City, where she performed in Graham's auxiliary performance troupe at Carnegie Hall. Blessed with striking good looks and a dancer's body, Betty also dabbled in modelling to keep her head above water. But her New York chapter ended when her mother convinced her to return to Michigan in 1941, where she taught dance to disadvantaged children and worked at a local department store.

Soon, Betty was dating a childhood friend, William Warren, who - like her father - was a salesman. But the romance was rocky and she broke off their engagement, only to reunite with Warren - possibly because her mother and new stepfather weren't fond of him. Their disapproval, Betty cheekily remarked, "made him all the more alluring to me".

The couple married on April 23, 1942, but the union ended after what Betty described as a "five-year misunderstanding". In reality, she'd tired of Warren's "cruelty" and being "moved from pillar to post" due to his frequent job changes - possibly brought about by his alcoholism. Betty sought a divorce - a brave move for the conservative postwar decade, when such action was rare.

Four months before the divorce was finalised, she was introduced to Gerald Ford at a cocktail party. The attraction was instant. He was handsome, a former football star, World War II naval veteran and a promising lawyer; she was pretty, determined and headstrong. Crucially, both had been raised with all-American values of decency and plain-speaking. Gerald revealed he was running for Congress, and they tied the knot on October 15, 1948 in Grand Rapids. Betty's status as an ex-dancer from New York and divorcee deterred Gerald only in that he delayed the nuptials until just before the November elections, fearing the saucier elements of her background might offend the more old-fashioned voters.

If they did, it wasn't in sufficient numbers, and Gerald became the Republican member for the Fifth Congressional District of Michigan in January 1949. The couple moved to Washington, DC, where they had the first of four children, Michael, in 1950. He was followed by Jack (1952), Steven (1956) and Susan (1957). All their children, Betty said proudly, "were brought up to think independently, the way I was myself".

The rigours of congressional work kept her husband away from home 200 days a year, and raising four children on her own - in the home in Virginia that the family moved to in 1955 - took its toll. In 1965, Betty suffered a nervous breakdown. "I saw my psychiatrist once a week, at the most, for a period of a year and a half," she admitted. It was yet another groundbreaking revelation during her time in the White House, and the admission helped remove the stigma of mental illness. "Somebody had to tell me what that doctor did: that I shouldn't just live for my husband and children, but ought to do something for myself, too."

Taking the advice to heart, Betty threw herself into charity work, while continuing to undertake the tasks of a congressional spouse. For the next 25 years, the Ford family shone as a beacon of unity. Behind the scenes, however, Betty was hiding a dark secret. Like her father and first husband, she, too, was an alcoholic - a problem that began on the political cocktail circuit and worsened in 1964 when she began taking up to 20 prescription pills a day for arthritis and a pinched nerve in her neck. Betty admitted she'd become "preoccupied [with] whether alcohol was going to be served" at night, and her children complained that she often forgot things.

Still, Betty was nothing if not tenacious, and claimed her drinking was never out of control. She managed to hold herself together for two decades, eventually looking forward to Gerald's imminent retirement and a move to California. Then history interrupted.

In October 1973, Vice President Spiro Agnew resigned amid bribery allegations. Gerald - whose integrity had won him bipartisan support in Congress - was endorsed as his replacement. "If I had known what was coming, I think I would have sat right down and cried,'' Betty revealed in her autobiography. What was coming took place 10 months later when Gerald had the US presidency thrust upon him after Richard Nixon was forced from office amid claims he covered up an attempted burglary aimed at sabotaging his Democratic opponents.

"I assume the presidency under extraordinary circumstances,'' Gerald said at his swearing-in ceremony on August 9, 1974. But while he embarked on a process of restoring honesty to the White House, Betty's candour and trademark outspokenness were causing havoc. When asked about presidential sleeping arrangements that had, until then, dictated the first couple sleep in separate bedrooms, she declared: "We had always shared a bedroom and I thought there was no reason we had to change our lifestyle." One woman, she said, "wrote in to say she thought it was disgraceful".

Yet from such controversy a star was born, and Betty truly seemed ahead of her time, even in an era that was defined by tectonic shifts in society. The '70s were marked by the march of feminism, and Betty embraced the cause, forever imprinting her character and courage on the White House. During her first official press conference on September 4, 1974, she declared her support for abortion rights, women in politics and the proposed Equal Rights Amendment to the constitution. She appeared on 60 Minutes in the US and proceeded to discuss premarital sex, teenagers and drugs. Initially, the public reaction was negative, but there was something intriguing about Betty's solid family values; her well-raised children; and her outgoing disposition.

Besides, she explained, "I wasn't forcing my opinions on anybody, but if someone asked me a question, I gave that person a straight answer." Her honesty worked. At the height of her fame, she was more popular than her husband in the polls, and even appeared in an episode of The Mary Tyler Moore Show, playing herself. By the time Gerald ran for president in 1976, her approval rating was at 75 per cent and campaigners wore badges saying "Vote for Betty's husband".

Gerald lost the election to Jimmy Carter, and Betty was happy to return to a private life, relieved that "our ordeal was over". But another was about to begin.

While she was able to conceal her alcoholism from the nation, Betty couldn't hide it from her family. They'd begun watering down her drinks and made excuses for her behaviour. Gerald admitted he was a "bad enabler". In 1978, a week before her 60th birthday, the family staged an intervention to help get Betty off the booze and pills that threatened to take over her life.

"I was very cross about it because I felt, 'Here I've spent my whole married life looking after my children and my husband, and how can they say these things and how can they confront me this way?'" Betty recalled in 2002. But the intervention saved her life. She went into rehabilitation and took part in group therapy sessions with five other women. They dubbed themselves "the sixpack". "You have to have at least some humour while going through this," said Betty.

She got sober and her husband quit alcohol in support. Her salvation inspired her to establish the Betty Ford Center in 1982, after she told friends that a rehab centre was needed that emphasised the special needs of women. At the time, men far outnumbered women in treatment, and Betty's centre in Rancho Mirage, California, changed that - providing equal facilities for women and men, including separate dormitories.

Betty worked tirelessly to raise funds for the centre, which has helped thousands of people, including stars Keith Urban, Elizabeth Taylor and Kelsey Grammer, in the past 30 years. "They helped me discover that I wasn't going to be much good to anybody unless I could figure out how to save me,'' the Frasier star said of the centre, where he beat drug and alcohol addiction in 1996.

Betty, who still lives near the centre in Rancho Mirage, sat on the board until 2005. Poor health has curtailed her public appearances and, although no longer in the limelight, her place in American history is well assured. In 1991, President George Bush honoured her work with the Presidential Medal of Freedom, and President Bill Clinton issued her and Gerald (who died at the age of 93 on December 26, 2006) the Congressional Gold Medal in 1999 - the highest awards available for public service.

When asked about her eventful life, Betty was typically understated. "I was an ordinary woman who was called on stage at an extraordinary time," she insisted. "I was no different once I became first lady than I had been before. But, through an accident of history, I had become interesting to people."