But far from living in a self-pitying cocoon of memories, she leads an active life which involves travelling the world putting on concerts and exhibitions.

Yoko Ono is most famous for being married to John Lennon

Yoko Ono, best known for being the widow of former Beatle John Lennon, seems indefatigable. After a lifetime of producing paintings, sculpture, short films and songs, she is planning to spend the summer going round her art shows in Europe, before beginning a new music CD in the autumn.

Yoko Ono has regularly been maligned and vilified by critics, who condemned her art as meaningless, her films as weird and her songs as tuneless.

Yoko Ono: "Art is a mind game"

But recently, she has begun to enjoy a reassessment of her work in the serious media. On Sunday, a programme on BBC Radio 3 attempts to discover whether her art has any lasting value.

In the public mind, Yoko Ono has became the woman responsible for breaking up the Beatles. The programme, called Yoko Ono: A Life In Flux tries to move away from that reputation and concentrate on what motivated her creatively.

Shock tactics

Aiming to express her radical feminism in art, Yoko shocked the public with acts such as inviting members of an audience to cut pieces from her clothing; opening an exhibition with a canvas to be stepped on; creating a film called Bottoms, featuring people's backsides; and in music, singing songs with titles such as I Felt Like Smashing My Face in a Clear Glass Window.

In exclusive interviews with Radio 3, the Japanese-born artist-singer and sculptor tries to explain her work.

"Art is a mind-game that we do to make our lives easier. If it isn't for that it becomes superfluous," she says.

She involved herself in a range of activities for the pleasure and the challenge it gave her: "Once something is solid, it's dead. I just like to explore all sorts of different forms - no, explore is not even the word - enjoy. You don't want to limit yourself to a particular form."

Music or screaming?

She still defends her famous bed-in in an Amsterdam hotel with John: "We didn't think we were naive, we thought that we had it all figured out. Maybe we were naive but I think that's the kind of naivety that may be necessary in life."

In the 1970s, she and John continued producing music. Critics condemned her bizarre singing as screaming.

She says: "I was doing very musically intricate things, in terms of rhythm and notation and how it moves. I thought it was comparable to someone like Schoenberg in terms of the structure of the music and they didn't hear that at all. They just said 'Yoko's screaming!'"

In the past couple of years, however, the exhibitions she has staged have been met with critical acclaim by intellectuals who argued she had been misunderstood and that her work deserved greater applause.

'Awful art'

But there are still some who insist that any appreciation of her work is a case of the Emperor's New Clothes - there is no substance involved, but in a new era of political correctness, it takes a brave soul to say so.

Brian Sewell, art critic for the London Evening Standard and television personality, said: "She's shaped nothing, she's contributed nothing, she's simply been a reflection of the times.

"I think she's an amateur, a very rich woman who was married to someone who did have some talent and was the driving force behind the Beatles. If she had not been the widow of John Lennon, she would be totally forgotten by now.

"Yoko Ono was simply a hanger-on. Have you seen her sculpture or paintings? They're all awful."

Mr Sewell says it was easy to become famous in New York in the 1960s by mixing with the right people, and that Yoko managed to keep a kind of mythology about her.

But he does not believe she has deliberately set out to the public into believing she was talented: "There is a point at which people begin to believe in their mythology," he says.

Artists 'are like trees'

After John's murder, Yoko Ono used the themes of death and mortality, such as an exhibition of coffins with trees where the heads should be.

Yoko Ono: "The boys club idea definitely existed"

"I could say that yes, there were a lot of ups and downs and a lot of hurt in my life, but in hindsight, it was a kind of education that I had to go through. From here on, I would like to learn without getting too hurt."

Yoko says: "I feel that my work is not in vain, that it does have a place in society, even though it may not be considered that it has a place in society - it doesn't matter.

"People don't remember each tree in a park but all of us benefit from the trees. And in a way artists are like trees in a park."

A Life In Flux hears from other critics, who variously talk of her joining an era of "conceptual art", who defend her singing as having a "post-blues controlled pitch" and who argue that she brought innovative aesthetic techniques to a mass audience.

But programme producer Lance Dann denies any pretentiousness, pointing out that the programme charts Yoko's work in a chronological way.

"It moves swiftly enough that if there's something difficult to understand the story moves on quickly.

"She works in an obscure form but the whole Brit-art scene of today was influenced by the 60s.

"I don't know whether she's a great artist but whether she is or not, she's an important figure."