It was the guilt at breaking off an engagement that indirectly led Sister Giles to become an enclosed nun. Twenty five years later she made the momentous decision to return to secular life, where she found a changed and bewildering world waiting for her.

Now she has charted her journey in two memoirs that explore both her spiritual life and the difficulties she encountered in navigating her way through modern life.

She humorously describes how she learned to drive, shop in supermarkets and visit the hairdresser after wrestling with the “torture” of hair rollers. The hairdresser’s was certainly an eye-opener.

“‘Would you like it layered?’ asked the stylist. I had no idea what she meant,” writes Sister Giles, who is now 83. “‘Oh, yes, please!’ I said hopefully. ‘I don’t like criticising the work of other hair stylists, but whoever did yours never did you a service,’ observed the hairdresser.”

She was unaware, of course, that Sister Giles had cut her own hair with nail scissors for years using the back of a Vaseline tin as a mirror.

At the first supermarket she visited, she was “amazed at the crowded shelves, the metal baskets and trolleys”. Driving lessons after her decades in the convent were a whole new experience.

“I was paralysed with anxiety,” Sister Giles recounts. “The three-point turn had taken at least sixteen.”

She had never thought she would become a nun, as Sister Giles puts it in the opening sentence of The End And The Beginning, her first memoir.

Born in Sussex, she grew up here, with her parents and sister. Her father left the family when she was seven and her sister two, propelling her mother into a writing career to support them.

Later, Sister Giles won a scholarship to a drama school but when she broke off an engagement at the age of 19 she found herself wracked with guilt.

Soon after she read an essay on Therese of Lisieux, the deeply spiritual French Carmelite nun who died aged 24.

She immediately “simply felt certain” that she should become a Catholic.

She took her vows and entered the convent of an Order that was considered the most penitential in the world. “Noviciate days of enthusiasm – and sometimes despondency – merged to a routine of prayer and work, recreation and laughter.

"Austerity bore no particular hardship after a time. Bare floors, a thick brown habit that almost stood up on its own, and odd conventions observed over centuries, became part of a life which was strangely fulfilling. Enclosure, for me, was never claustrophobic.”

But one July morning 25 years later, Sister Giles walked into the convent garden and a sudden feeling overcame her.

“I’m not given to interior voices,” Sister Giles writes. “I have never heard one.

It was not a voice, as such, that I heard.”

But as Sister Giles tells Sussex Society, “I felt compelled to do this thing. I have had that in my life quite a bit – I get a great sense that that has got to happen.”

She was granted unusual permission to remain consecrated, yet released from community life. So she left dressed in trousers donated for work in the garden and a grey anorak she had made in the convent vestment room.

It was “more than an adventure” and after three days sister Giles decided to remain in the secular world, where she helped a friend to run a retreat where people could go to be refreshed spiritually.

It was a calling that she has continued to follow in the 23 years since leaving the convent, offering help to many people in her new life.

She tells Sussex Society, “I have never regretted leaving the convent. I had no money, but somehow my friends have offered me the most remarkable gifts just when I needed them.”

Those gifts included a house left to her in a will, the sale of which enabled her to buy the cottage in Petworth where she now lives.

Her faith remains constant and Sister Giles prays every day.

“Sometimes, I feel a nostalgia for what seems so foreign to values paramount today,” she writes in her second memoir Circle Completed.

“But I believe that nothing whatever need separate us from the love of God.”

The End And The Beginning and Circle Completed, both by Sister Giles, are available priced £14.95 and £9.99 respectively, published by The Memoir Club. For copies call 01388 529060, email memoirclub@email.msn.com or visit www.thememoirclub.co.uk.