It was a promise to her dying husband that finally made Mary Nickson pick up her pen and write after years of prevarication, she tells Sharon Griffiths.

THERE is something glorious about reinventing oneself at 72. And writer Mary Nickson has done it in style. After four novels as Mary Sheepshanks and a four-year gap following a nasty accident, during which she did no prose writing at all, she is back with a new name (actually her maiden name) and a huge, multi-layered, very readable novel of love, loss and family life, all set in an intriguing house in Corfu.

The only problem is that it's hard to believe her age - and not just because she looks ten years younger and is wearing jeans the colour of crushed raspberries - but because of her energy and enthusiasm as her conversation skips and leaps from the Romanovs to Ilkley Moor, via autism and leaking roofs and - most often - her family of children and grandchildren, one of whom christened her his "wild writing granny".

Mary Nickson is a terribly English combination of rather grand - she was brought up at Eton and had dancing lessons with the Queen and Princess Margaret - and utterly down to earth. It's a beguiling mixture.

Although she'd been a writer since childhood, life - including early marriage, children, running a school and then a big house with a rare John Carr staircase and that expensively leaking roof - got in the way of ever getting anything to a publishable state.

"I should have written a book before, but I was too wet. I was looking for excuses not to do it because I was scared of failure I suppose," she says.

Mary also had other priorities. Her husband, Charles, who was 20 years older, had a long illness, but just before he died, she asked him if there was anything he wanted to do, anything he wished for.

"His one passionate wish, he said, was that I should write," she says. "After doing things for other people, he wanted me to do something for myself and he made me promise that I would."

After his death, Mary moved from the large, leaky house near Harrogate to a smaller, sounder one, seven miles away with stunning views.

"And I made myself write. At first I kept putting it off. I was quite feeble and kept finding excuses not to try. But in the end I had to do it - because I'd made a promise to Charlie that I would. And I found that I loved it," she says.

Which only goes to show what a clever and kind man her husband must have been.

An agent looked at her first effort and told her it maybe had something, but would have to be rewritten - which took 18 months. But it was worth it. Mary had her first novel published when she was 62, a fine encouragement for late starters.

"When I saw the first copies of that first novel, I was absolutely euphoric. Then I cried and cried because Charlie wasn't there to share it with me."

Mary's new novel - a great big book - is set in Corfu, an island she knows well. "We've had many family holidays there over the years with children and grandchildren." Although set in the present, it stretches back to the war and involves four generations of a family.

The main character is a young widow, who discovers after her husband's death that he was not the person she thought he was.

"I wondered what that would be like, to discover that you were mourning a man who in a way never existed. The idea intrigued me."

Otherwise, she says, she writes of things she knows. And what she doesn't know, she finds out about - which for the book involved a long and fascinating e-mail correspondence with an authority on Greek icons.

The plot also hinges on a tale of two silver boxes, kept by separated lovers for over 50 years. Highly improbable.

"But actually based on a true story in my family," says Mary. "I was brought up on the story of my eldest uncle, a very dashing war hero, a double MC, who fell in love with a red-headed Canadian girl. He was on his way to marry her when she told him she was marrying someone else. He was heartbroken.

"He never married. But two generations further on the families were united after all. My eldest daughter married the Canadian girl's grandson. Very strange and more than chance, you would think."

"The Venetian House" is based not on one particular house, but a number of houses in Corfu, and the story - while eventually ending happily - has plenty of dark and shade to give it depth and richness, making it much more satisfying.

And maybe that's the difference between chick lit and the novels of seventy-somethings. The grown-ups have simply lived more, seen more and understood more of what life is about, of the complexity of relationships. After the glib flipness of so many pastel-covered novels by 25-year-olds, it comes as a blessed relief.

Mary Nickson - as Mary Sheepshanks - is a published poet. As well as in a number of slim volumes, her poems are also published regularly in The Spectator. "Poetry is my real love, my passion," she says.

Her work covers a wide range, from haunting, moving observations on life, through images of Mrs Noah, lumbered with doing the cleaning up after The Flood, to the sort of verse which you can - and she does - hang in the loo. (In fact, she has so many interesting poems, drawings, books, magazines and pictures in her loo that you could cheerfully stay in there for an embarrassingly long time.)

Mary has also written a book about coping with grief. "I lost a baby daughter and a husband, and was asked to write about bereavement," she says. "I didn't want to at first, but they asked me again, so I did it. It's not a guide book, but reflections on the mourning process. It's out of print now but I still get letters from people who have found that it helped them, which is very touching."

But although, at 72, Mary Nickson has a grown-up perspective on life, she is also still in the thick of it. Her novel is not some nostalgic wallow, but very firmly here and now. It has some very real children and clubbing teenagers in it. Mary's eight grandchildren range in age from seven to 24 years old and she delights in their company, and that of her children, and seems very good at swooping down on starving students and taking them out and feeding them generously. "The bonus of marrying and having children young is that you then become a young grandmother and can enjoy your grandchildren so much," she observes.

And, in between, she is already well on with her next novel, enthusiastically detailing intricacies of plot and people. There are doubtless more to come - as well as more poetry.

Mary has, like most people her age, had her share of tragedy and sadness.

"But to have had this new life, this new career as a writer so late in life, is a real bonus," she says. "I am fantastically lucky."

* The Venetian House by Mary Nickson (Century, £10.99).