“I have no fear of death,” Katharine Hepburn said at the end of her 1993 television autobiography, All About Me, and you believed her. The voice wavered from the creep of Parkinson’s Disease, but she was still powered by the dauntless self-confidence that defined her as much as that strident Bryn Mawr accent. Her eyes still sparked fire. “Must be wonderful,” she continued, no-nonsense, “like a long sleep. But let’s face it: it’s how you live that really counts.”

Hepburn, who died June 29 2003, aged 96, lived on her own terms, and made her mark playing women who did the same, when this counted as an act of subversion. The vitality of her great performances of the 1930s and ’40s still sings, singes and stings. Take just Bringing Up Baby (1938), Howard Hawks’s definitive, machine-gun paced screwball comedy, with Cary Grant as the mild academic who likes playing with dinosaur bones, until Hepburn’s unstoppable society girl – with a leopard for a pet – slaps him awake to life with the relentless force of her freedom.

Cinema’s first incarnation of modern, independent woman, wits as sharp as those incredible cheekbones, it’s not stretching the point to suggest Hepburn did as much as anyone to further the idea of feminism. Simply by refusing to be anyone but herself, she carried the war of the sexes onscreen.

The second of six children, she was raised on her beloved Connecticut coast in a distinguished New England family whose affluence and free thinking engendered her steely nerve, independence and artistic flair. Her father, a surgeon, dedicated himself to the then-unspeakables of venereal disease; her mother was a public speaker, an advocate of contraception and women’s rights. As a tomboy child, Hepburn walked alongside her on suffragette marches.

The parents encouraged physical discipline – a lifelong sportswoman and athlete, Hepburn was still swimming in that ice cold east coast sea well into her late 80s – strong morality and spiritual liberation. But childhood showed her a darker, more vulnerable side of life too; when she was 14, her 16-year-old brother hanged himself. She discovered the body.

She first arrived on Broadway as a budding 21-year-old in 1928, and earned a reputation as trouble for speaking her mind – but also as a prodigious talent. Great success in the lead of a 1932 production of The Warrior’s Husband led RKO to ask her to name her own price for a contract. In Hollywood, she caused publicists to throw up their hands, disregarding their image making attempts to walk around in her soon-iconic floppy trousers, or slouch in overalls, cascades of auburn hair tied in a knot. She shunned interview opportunities and Tinseltown parties to keep company that genuinely engaged her mind.

She started in movies a star, making a stunning debut as John Barrymore’s daughter in A Bill of Divorcement (1932). The director George Cukor became a lifelong friend and collaborator; they made nine films together, the last, The Corn is Green, in 1979.

The first of her four Oscars came with her third movie, Morning Glory (1933) – although it was her fourth film, playing the definitive Jo in Cukor’s Little Women (1933) that was her first great personal screen triumph. A return to Broadway for The Lake, however, was a failure, provoking that frustrated actress Dorothy Parker’s famous jibe: “Miss Hepburn ran the gamut of emotion from A to B.”

In retrospect, her glory years began with her run as the dissatisfied, sophisticated spitfires in Stage Door (1937), Holiday (1938) and Bringing Up Baby, but that last insane masterpiece was a flop in its day. The year it came out, Hepburn’s name appeared alongside Joan Crawford’s (a different kind of independent woman) on the notorious list of “box office poison” drawn up by film exhibitors. That, and David O Selznick’s decision to reject her as Scarlett O’Hara in Gone With the Wind (1939) pushed her back to the Manhattan stage, where she firmly took her career back into her own hands.

The play, written for her, was The Philadelphia Story, and she was Tracy Lord, another beautiful society girl with a hellcat temper and a sulky pout that could tremble into tears or break into ravishing laughter. It was a major hit, and she owned the rights, bought for her by former lover Howard Hughes. Taking the film to MGM, at a price, she dictated the movie, picking the director, Cukor, and her co-stars, Cary Grant and James Stewart. Released in 1940, the film set new box office records. It looks better every year.

Already blurred, real life and onscreen life became indistinguishable with her next movie, Woman of the Year (1942), first of her seven films with Spencer Tracy, and the start of their fabled, 25-year love affair. He was married and never divorced but, while the relationship was an open secret – Cukor gave them the guesthouse of his Hollywood estate to set up home – the same public who would later hound Ingrid Bergman out of the country over an affair adored them. The couple commanded such respect that even the rabid Hollywood gossip columnists left them alone.

The Tracy-Hepburn movies were mostly wonderful, sparky sparring matches, abrasive and tender. Her greatest onscreen partnership of the period, though, was with Humphrey Bogart, as the spinster schoolmarm accompanying his unwashed steamboat captain up the Congo into the heart of sweetness for The African Queen (1952). That, an extraordinary performance as the monstrous matriarch of Suddenly Last Summer (1959) and a staggering one as the addict in Long Day’s Journey into Night (1962) were all deserving of another Academy Award, but that didn’t come until Guess Who’s Coming to Dinner (1967), a worthy but lifeless affair, and her last film with the ailing Tracy, who died 17 days after filming wrapped.

She rallied, picking up another Oscar the following year as the embittered, exiled queen in A Lion in Winter (1968). Hepburn was now into the grand old lady stage of her career, but as if to keep the world on its toes, at the age of 62 she veered back to Broadway again to make her singing debut in Coco. The films came less frequently, but there was another Oscar opposite another peppery old grouch, as Henry Fonda’s wife in the valedictory On Golden Pond (1981), filmed in the New England countryside she had lived with and loved since she was a girl. Fonda died soon after the film was made; Hepburn, at 74, fought off a stunt double to insist on diving into an ice-cold lake herself for one scene.

She became an author in 1987 with the self-explanatory memoir, The Making of the African Queen: Or, How I Went To Africa With Bogart, Bacall and Huston and Almost Lost My Mind. Her second book, the remarkable 1992 autobiography entitled, simply, Me, was a bestseller around the world. Still she wasn’t finished. In 1994, a frail but feisty Mother Goose, she returned to the movies for Love Affair, and in her few scenes comprehensively showed up Warren Beatty and Annette Bening.

Three nights after she died, the lights along Broadway dimmed to mark her passing. “It’s how you live that really counts.” A fine epitaph; but you suspect Hepburn might have preferred the line with which Tracy lovingly summed her up half a century ago in Pat and Mike (1952):

“Not much meat on her; but what there is is cherce.”