A grande dame who won't conform

An unprecedented tribute from the Academy of Motion Pictures in mid-November and, earlier this week, a Best Supporting Actress gong at the British Independent Film Awards for her overpowering performance as Volumnia, the iron-willed matriarch in Ralph Fiennes's film version of Coriolanus. Not to mention all those reviews raving about her deeply funny and touching portrayal of a cantankerous, blinkered Southern matron in the West End hit, Driving Miss Daisy. It's been a season of luxuriant bouquets for Vanessa Redgrave. But there have been brickbats, too, and you cannot get to the essence of her art unless you also take these into account.

On the one hand, the Oscars travelled to London for the first time ever to mount an evening in honour of her 50 years in film. It was hosted by David Hare, who praised her "ability to make thinking look fun, to lend glamour to thought as much as to feeling. In her performances there is an interior quality which has been much remarked... the sense that the emotion or conviction is drawn up from a deep, almost inaccessible place. But less remarked is the shine she then puts on it. It is as if she both draws light and reflects it."

On the the other hand, she was mocked in a broadsheet showbiz column as a self-involved, interfering "celebrity angel of death" whose visit to meet and defend the Dale Farm travellers' site would virtually guarantee their eviction from the Essex site.

That phrase was unfortunate, given how well-acquainted with angels of death the Redgrave acting dynasty has become in the past few years. Natasha Richardson, the older of her two actress daughters by director Tony Richardson, was cut off in her prime in March 2009, after a skiing accident – followed a year later by Vanessa's brother Corin and her sister Lynn.

It's typical of the actress's idealism and guts, though, that, just seven months after the untimely loss of Natasha, she fulfilled a commitment to reprise her role in The Year of Magical Thinking, a solo show based on Joan Didion's intimate memoir of her struggle to come to terms with the death of her husband and the fatal illness of her daughter. Hair scraped back in a ponytail from the long, gaunt face that is matchless in its emotional transparency, Redgrave had triumphed in the part on Broadway and in London. But now the subject matter was horribly close to home.

Putting duty before personal feelings, she pressed ahead. Staged in New York's Cathedral Church of Saint John the Divine, it was a benefit performance for causes important to her – Unicef (for whom she is a Goodwill Ambassador) and UNRWA, the agency that helps Palestinian refugee families. At the Oscars tribute evening, her friend Eileen Atkins said that "courage" and "radiance" were the two words most used about Redgrave. "And I think," she went on, "that comes from her true belief that basically mankind is good. She believes in humanity, and not many people do."

This remark pierces to the heart of the actress's greatness and also implicitly explains why her genius will always remain controversial.

In his review of her brilliant performance as Lady Torrance in the Peter Hall production of Orpheus Descending, the critic Frank Rich rightly observed that Vanessa Redgrave and Tennessee Williams are made for one another because they both "run at life bravely, openly, without defences and without fear of their inevitable destruction, like great, beautiful deer bounding across a highway after dark".

Her movie career took off with her portrayal of an enigmatic Sixties swinger in Antonioni's Blow-Up (1966). More than 100 films, six Oscar nominations and one win (for Best Supporting Actress in Julia) later, we can now rejoice in the wealth of her superlative recent work. It's hard to conceive of more powerful acting in merciless close-up than that which Redgrave produces in the coda to Atonement, where she plays the elderly, dying Briony under polite interrogation from a TV interviewer.

Redgrave was catapulted to glory as a stage actress by her gamin, free-spirited Rosalind in a 1961 production of As You Like It at Stratford. The critics went into rhapsodies, with Bernard Levin gushing that, "This Rosalind is a creature of fire and light... her body a slender supple reed rippling in the breeze of her love, etc etc."

Redgrave's political activism has sometimes been questionable, especially during her days as a leading member of the Trotskyist Workers' Revolutionary Party, and it has sometimes been costly. But you can't deny that the activisim is intimately connected to the lit-from-within quality of her acting and its impetuous ardour. And even now, Redgrave could never be categorised as "national treasure". She is, to her credit, too angular and unbiddable.

And she cannot be understood except in relation to her family. The tabloids, of course, slapped the stupid "Curse of the Redgraves" label on the recent spate of tragedies that have befallen the clan, the implication being that any brood spawned by a Leftie and practising bisexual, as the great actor Sir Michael Redgrave was, deserves all that is thrown at it. Corin, her fellow activist, wrote a wonderfully empathetic memoir of their father, in which he explored the cost to Michael, his wife, Rachel Kempson, and their family of the double life he was forced to lead because of his outlawed sexuality.

It's not through nepotism but through inherited gifts and a sense of natural succession that Natasha and Joely have so often played the daughter or younger self of the characters portrayed in films by Vanessa (Joely is doing this at the moment as Elizabeth I to her mother's wily old monarch in Anonymous). And next year, at the Rose Theatre in Kingston, Joely will follow in the footsteps of Vanessa and her late sister who both won resounding acclaim as Ellida, the heroine in Ibsen's The Lady from the Sea.

Laurence Olivier announced Vanessa's arrival in the world from the stage of the Old Vic where he was playing Hamlet with a cast that included her father: "Ladies and gentlemen, tonight a great actress has been born. Laertes has a daughter." The Best Actress nominations are starting to come in for Driving Miss Daisy and she is being tipped for an Oscar for Volumnia in Coriolanus. Seventy-four years later and with no sign of slowing down, Vanessa Redgrave is still peerlessly proving the truth of Olivier's prophecy.