To authors, a literary agent is many things — adviser on narrative, writing technique and plot, a shoulder to cry on, but above all someone who brings in a living wage.

Oxford professor Diarmaid MacCulloch, who found himself a TV star thanks to literary agent Felicity Bryan, summed up her role: “Felicity and her colleagues are not just a means of terrifying publishers and doing the hard-nosed negotiations that would send us delicate wilting flowers in the writing world reaching for our smelling-salts.

“They make us think further than our own limited visions: they show us possibilities which we had not glimpsed, and then they help us turn them into reality.”

Until 1998, English writers had to make their way to London to hear the good news that their first novel had been picked from the 'slush pile' and secured an eye-watering advance from publishers.

London may still be the undisputed centre of English literary life, along with the associated gossip and back-biting, but for the past 25 years Oxford has been mounting a modest challenge with Felicity Bryan Associates, based in North Parade.

Before branching out on her own, Ms Bryan was commuting each day from Kidlington as director of Curtis Brown, one of the UK's oldest and biggest agencies, which had represented most of the authors of the 20th century, from Wind In the Willows author Kenneth Grahame to war leader Winston Churchill.

At a party at the Ashmolean Museum to celebrate her agency's 25th birthday, she recalled the horror of her husband, the economist Alex Duncan, when she told him she was thinking of giving up work to spend more time with her three young children.

“I was on the train from Paddington, balancing a manuscript on ‘Sequencing’, which suggested that women were now confident enough in their careers to take time out for childcare. I told my husband that we would save the train fare and that I would not have to ‘dress for success’.

“I can still see the look of horror on his face. He knew that I would be no good around the house and that the world of books and authors is my lifeblood. He told me that I must set up an office in Oxford.”

It seemed a bold move at the time, but she was careful enough to negotiate a deal to bring some of her authors with her, including food writer Mary Berry, biographer John Julius Norwich and novelist Rosamund Pilcher.

Ms Bryan's background in art history — she studied at the Courtald Institute in London — led her to promote Oxford author Iain Pears's bestseller An Instance of the Fingerpost.

Since then the agency has grown to employ nine people, and expanded its range into children's books and movie rights. Catherine Clarke and Caroline Wood are now shareholders of the agency, with Sally Holloway an associate agent.

Authors at the party attributed its success to an uncanny knack of picking books that people want to read.

These include Edmund de Waal's The Hare With Amber Eyes, which the agency patiently pushed on to the market, despite the initial lack of interest from publishers.

As well as Mary Berry, other authors who have passed the million-copy mark include David Almond, whose first children's book Skellig was picked up by Ms Clarke and went on to win the Carnegie and other prizes. Now, 15 years since its publication, Hodder has bought the rights to his two new teen novels.

Its Oxford base has led the agency to bring several academics out of the ivory tower and into the world of commercial publishing.

Prof MacCulloch, author of The History of Christianity, said the agency had caused him to think more boldly than he would have done on his own.

"There I was, writing pleasant enough stuff about the English Reformation, when Felicity came along and swept me off my feet. Away with that, she said. Someone else can do it."

Other Oxford University academic authors include Tom Moorhouse, an ecologist at Oxford University's Zoology Department, creating a buzz with a children's book about his pet subject.

"They say, 'Write about what you know'," he said, "and I just happen to know about water voles."

Another zoologist, animal behaviourist and first-time author Corri Waitt (who runs the Farm Ability scheme at the University Farm, Wytham, has set the publishing world clucking with The Wisdom of Chickens, a popular science book due out in 2015.

The agency also has a rich crop of Oxfordshire children's authors, including Julie Hearn and Katherine Langrish.

Anyone earning their living from writing can only dream of a film deal, and the agency has secured a major success for Meg Rosoff with the release this month of the film based on her first novel, How I Live Now, inspired by the author's experience of living at St Frideswide's Farmhouse in Water Eaton, near Kidlington.

Professor MacCulloch said: "I know that the agency is a successful commercial enterprise, but it is also a group of delightful, creative and generous people who have helped us become better authors as well as richer authors.

“They love books, and they may even love authors, just a little bit."