A Vanessa Redgrave production...

starring Chechnya's Laurence Olivier and £50,000 bail. Co-starring the Elgin Marbles, the Workers' Revolutionary Party, victims of the 'Kursk', Lynn, Corin, Joely, Natasha and a cast of thousands...

If Vanessa Redgrave is brave enough to open the door of her west London flat over the next few days, there's every chance she will find an army posted outside. At 65, and with granny specs now frequently perched on her increasingly hawkish nose, the self-proclaimed Sixties revolutionary has plonked herself squarely back on the political frontline.

To anyone who ever doubted her continued commitment to radical humanitarian causes, the news conference she gave on Friday will have come as a rude awakening.

Khaki cap perched above her clear blue eyes, shimmering with youthful zeal, Redgrave could have been 30 years younger. What set her apart from her earlier self were not the tell-tale creases around the mouth, the greying temples or the sober dress. Rather, it was her air of almost presidential confidence – a form of eminence that can only be grown into with age and experience. Casting those fiery eyes around the rehearsal room of London's Royal Court theatre, Redgrave was in her element. She was there, she declared, to refute the "grotesque" allegation that she had been sheltering a suspected Chechen warlord from international justice.

Instead, she argued, a momentary quiver in her voice, Akhmed Zakayev was "Chechnya's Laurence Olivier", a peerless actor cruelly scapegoated by a Russian administration desperate to salvage dignity from years of conflict in the former Soviet dominion. Gesturing towards the vacant seat beside her, she spoke of the "truth" that had yet to "arrive in London", a truth that would vindicate her friend, proving him to be the moderate force for good she knows he is.

It was a vintage performance. At once, it was a reprise of the younger Redgrave, the defiant woman who marched the streets in protest at everything from the plight of Hungarian refugees to the 1968 imprisonment of child psychologist Dr Spock. But while it will have appealed to fellow travellers of her revolutionary causes, Ms Redgrave's speech will have won her few new fans at a time of terror-induced jumpiness. And it will have provided renewed succour for the tabloids, whose attention has more recently been directed towards her photogenic actress daughters, Natasha and Joely Richardson.

When Redgrave was born in January 1937, her future seemed assured. Olivier himself famously interrupted his curtain call after a performance of Hamlet at the London Old Vic with the declaration: "Tonight a great actress was born. Laertes has a daughter."

The Laertes in question was, of course, her father, the late Sir Michael Redgrave, then one of Britain's most promising stage actors. Redgrave herself would be the first to admit she had a comfortable upbringing. After attending Queensgate School, she studied at London's Central School of Music and Drama. At first she wanted to be a ballet dancer. In the end, it was her height that did for her (she now stands at a regal 5ft 11in).

Like so many other things in her life, Redgrave's film debut at 21 owed much to her family links. It was to be in the 1958 movie Behind the Mask, in which she played the daughter of a teacher, a role taken by her father. In 1961, she was invited to join Sir Peter Hall's Royal Shakespeare Company, then in its infancy. Within months, she had won acclaim for her performance as Rosalind in As You Like It.

During the Sixties and Seventies, she carved out a career as one of Britain's, if not Hollywood's, most accomplished and daring stars. She appeared in some of the era's defining movies: Antonioni's Blow-Up, Ken Russell's The Devils, and The Charge of the Light Brigade, directed by her then husband, Tony Richardson. Her ascent was accompanied by a string of Oscar nominations, for Isadora, Mary, Queen of Scots, The Bostonians and, most recently, Howards End. She won only one, appropriately enough, for Julia, an overtly political movie about the Jewish-American playwright Lillian Hellman's attempt to smuggle money into 1930s Germany to help fund the anti-Nazi cause.

While Redgrave's international standing is now lower than it was two decades ago, she remains prolific. In the last two years alone, she has made more than a dozen films and, though many of her roles have been cameos, there have been notable high-points. The awkwardly titled US TV mini-series If These Walls Could Talk 2 earned her best supporting actress Emmy for her role as an ageing lesbian.

On stage, however, there have been signs that her crown is slipping. Her appearance earlier this year alongside her younger daughter, Joely, in Lady Windermere's Fan was mocked by critics, with Ross Brooks, one of the play's former cast members, dismissing it as "below even the worst amateur standards".

Despite her undoubted achievements as an actress, it is as a bit player on the political stage that many will remember her. Her championing of humanitarian causes has won her many plaudits. In a recent interview, David Harewood, the star of the acclaimed BBC2 drama Babyfather, was effusive in his praise for the woman, 29 years his senior, with whom he had a much-publicised, albeit brief, liaison. "She inspired me," he said. "She made me think about things – issues, books, politics."

Yet for everyone willing to defend her inflammatory statements about the Chechen war and the PLO, there are legions of detractors. Redgrave's slavish devotion to the Workers' Revolutionary Party – an affiliation also held by her brother, Corin – has seen her variously branded a dangerous subversive and a harmless fruitcake. While co-starring with her in Three Sisters during the Gulf War, her sister Lynn Redgrave once said her sibling's political heroics were "driving me crazy". And the Russian concert pianist Nikolai Petrov dismissed her interference in his country's affairs with the words: "Please, mind your own business."

Some accuse her of hypocrisy. Unlike Lynn, she has always refused to be honoured by the Queen, but much of the personal wealth that enabled her to pay the £50,000 surety to keep Zakayev out of jail, or send three weeks' salary to families bereaved by the Kursk submarine disaster, has trundled out of the capitalist Hollywood machine.

Even her admirers have reservations. While they may be happy with her fund-raising for Aids sufferers and displaced Yugoslavians, her periodic defence of the IRA is, for many, a step too far.

Many of Redgrave's recent protestations suggest she has come to favour a more pragmatic approach to change. In 1997, she abandoned Labour, the party she had voted for throughout her adult life, defecting to the Liberal Democrats. But by 2001 the old fire was back. Within weeks of finishing in the National Theatre's acclaimed run of The Cherry Orchard, she was sharing a platform with Michael Roche, Britain's sole Marxist Party general election candidate. More recently, she persuaded fellow actors, including Dame Judi Dench, to back another hobbyhorse: the campaign to return the Elgin Marbles to Greece.

While it is easy to be distracted by the politics, some prefer to focus on Redgrave's acting. Lord Puttnam, the Oscar-winning producer who worked with her on the Agatha Christie biopic Agatha, describes her as "the most professional person I have ever worked with". Referring to her political beliefs as proof that she is "true to herself", he said: "She was the best prepared actress I ever knew. She never came into rehearsals without being totally in character."

Whether her stand over Chechnya – a long-time cause célèbre – marks the last gesture of a chattering-class warrior, or a glimpse of crusades to come, is, for the moment, uncertain. But it is hard to imagine her succumbing to dotage without a fight.