On September 19, Edmund Capon, the director of the Art Gallery of NSW, held a media conference to announce that after weeks of international negotiations, he had acquired Paul Cezanne's post-impressionist painting Bords De La Marne for $16.2 million. This was the culmination of a 30-year dream by Capon to secure a significant work by Cezanne. It is the most expensive work ever bought by an Australian public gallery.

Also at the announcement was artist and benefactor Margaret Olley, who signed a personal cheque for $1 million. This was the result of a promise made before Capon went on his quest.

"I told him before he went on holiday that if he found a Cezanne I would give him a million dollars," she says. The money was the proceeds from her latest exhibition, kept in an art trust for this purpose.

Olley, now 86, has been a prolific patron of the visual arts throughout her life. This donation is perhaps her most dramatic gesture, done in public to inspire others also to donate to the cause. About 85 per cent of the price of the painting has been raised so far.

Olley has also donated either her own work or examples from her private collection to regional and metropolitan galleries throughout her life, usually without any fanfare. In an age where investing in art has become a national obsession, here is someone who happily gives hers away.

"There is no more passionate supporter of the arts in this country than the indefatigable, ever-inspirational Margaret Olley," Capon said in 2006, when she was honoured in the Queen's Birthday list for her services to art. At the time it was estimated that she had given the Art Gallery of NSW 130 works worth about $7 million, including important lithographs by Picasso, Cezanne and Bonnard. In 2005 she donated a colour drawing by Edouard Vuillard which she had expressly purchased for the gallery.

Yet Olley comes from a humble background, being raised near Lismore during the Depression. As a young child she remembers not getting any pocket money unless she made her bed. As a student in Sydney she paid her way through art school by grape-picking and painting theatre sets for two shillings and sixpence an hour.

"I learnt generosity at my mother's knee," she says. "My mother and father were the most generous people. My father caught more fish than we ever needed, so he gave the rest away to neighbours. He grew his own vegetables, so he gave them away as well. I learnt from them that giving is much better than receiving."

She has had periods of great struggle. She once bought a small property near Newcastle and paid it off through her painting. This was before her work sold for anything close to today's values and she came close to losing the place.

She recalls sleeping with the cheque-book open next to her so that she wouldn't forget to make the next repayment. "I worked hard to make myself independent by painting," she says. "If you're doing what you want to do, it doesn't cost much to live."

Her paintings are now in the blue-chip category but she still prefers a simple life, part of her philosophy for happiness.

"As you get older, you move to a point where you can give back to society," she says. "The world would be a much better place if all the retired teachers, accountants, plumbers and butchers were encouraged to give back a little bit of their knowledge to society."

Giving back is what she has done by helping fund the acquisition of the Cezanne painting. She calls it the most important work in the gallery and hopes it will inspire a new generation of artists in the same way that his work inspired her as a young woman. She sees it as a great investment in social as well as financial terms.

"My donation is just the beginning," Olley says. "I hope that everyone gives what they can."

The big questions

Biggest break When I came down from Lismore and went to East Sydney Tech [now the National Art School].

Biggest achievement Handing over the money for the Cezanne is the most important thing I have done. I've never written a cheque for a million before. I had to ask Edmund: how many 0s?

Biggest regret None. Regrets are a waste of time.

Best investment Friendships. Unfortunately I've always preferred the company of older people, so that makes it pretty difficult at my age.

Worst investment Buying that property in Newcastle, I suppose. I'm much happier living here in Sydney.

Attitude to money It's only paper, isn't it?

Personal philosophy I don't understand the current obsession with the "me" and the "I". The best way to exist is to forget about yourself and just get on with it.