MARY ZACAROLI celebrates Mills and Boon's 100th birthday as part of the Oxford Literary Festival 2008

The publisher Mills & Boon celebrates its 100th anniversary this year. Started by Gerald Mills and Charles Boon in Covent Garden, having published such diverse authors as Jack London, P.G.Wodehouse and Shakespeare, the two men found their forte was romance. After merging with Canadian company Harlequin in the early 1970s, it is now the world's leading publisher of romantic fiction.

More than 50 new Mills & Boon titles are published a month. Their most popular line is Modern, but for those who want more bang for their buck there is Blaze and the newly-launched Heat. More traditional romances are covered in Romance, while Historical Romances satisfy another market. Then there's the Medical line, which can be surprisingly realistic about life in UK hospitals. And that's only about half their monthly output. Translated into 26 languages, the company sells 200 million books worldwide each year and has more than 1,300 authors.

For its centenary, it is publishing a wide variety of books and also sponsoring an event at the Oxford Literary Festival. Joanne Harris, Katie Fforde, Matt Dunn and Nicola Cornick will debate how heroes and heroines have altered over the past century. Their chair will be Daisy Goodwin, the TV producer and writer, who partly covered this topic in last year's BBC documentary Reader I Married Him.

Nicola is the only Mills & Boon writer on the panel. A former university administrator, she used to read Regency romances and eventually tried writing one. Twelve years later, she got published and, ten years on, she recently completed her 28th title. What does she think that readers are looking for from her books?

"I think it's to be able to escape," she said. "That's one of the great things about historicals, because history is already a fantasy world. The appeal of the romance is very strong and to know that that's going to have a happy ending is absolutely essential.

"There's something to do with myths too - really powerful fantasies that aren't just in romance stories, but in all kinds of books. And obviously the conflict between the characters is what drives the story on."

Her fans range widely in age and occupation. "Although they are predominantly female, there are some male romance readers who don't mind admitting it," she said. "I've had a lot of emails from professional women who half shame-facedly admit to loving reading romance books."

That brings the topic on to the sometimes vitriolic attacks that the company has faced over the years. It has been accused of giving women unrealistic expectations of relationships, being misogynistic and, the ultimate insult, being formulaic.

"They're confusing formula with myth archetypes," said Nicola, who recently completed an MA at Ruskin College. "There are certain myths in storytelling which person reading or hearing it expects to be in there; the happy ending is a good example. If you're reading that particular type of book or hearing that story, that is your expectation as a reader. And that is what gets confused with formula, yet within that structure you can have all kinds of stories."

She thinks the people who criticise Mills & Boon are judging it on something that it was never intended to be in the first place.

"I don't think anybody setting out to write a Mills & Boon romance is setting out to write something that is comparable, nor would want it to be comparable, with a literary' work. "You're writing something that is in a different style. You're writing a story that is going to mix elements of reality and escape and myth into one fantastic romantic story that people can lose themselves in. You're not aiming at writing a Booker Prize-winning novel, but I think the people who judge it are doing that."

For the centenary, she was asked to write a novel set in 1908. The result was The Last Rake in London which concerns the roguish Jack Kestrel, who wants to steer a relative away from the flighty sister of nightclub owner Sally Bowes. Nicola usually writes Regencies, so she found it an odd experience.

"There were motorcars and the tube. A lot of stuff felt too modern when I looked into it, but I think it was pretty close to a Regency, which isn't to say that it's not accurate." It is good fun to read, however, fulfilling all the criteria that Nicola outlines above.

I admit to being a fan of M&B. They've kept me happily occupied in recent years with their tightly focused, sometimes astonishingly dark, stories. They are certainly not pink and fluffy. What the company does is cater to all kinds of readers, serving up what they want over and over in innovative ways. In my book, that's something to be celebrated. So happy anniversary Mills & Boon.