I am discussing football with Joanna Trollope – specifically, her love of Chelsea FC. She’s a huge fan, it turns out, and likes nothing more than heading off to the mid-week games to cheer from the terraces.

It shouldn’t be a surprise really – if it’s good enough for Delia… nonetheless, there’s something rather amusing about the thought of Trollope, with her cut-glass tones and perfect blonde highlights, bellowing away at a match.

I wonder how her fellow supporters react when they spot one of the UK’s bestselling authors in their midst?

“Oh well, I usually have my hat pulled down,” she says with a chuckle. “The whole point is being anonymous.

You do get the odd sideways look now and again but there’s no question of any sort of nonsense. Everyone’s there for the game.”

She’s delightfully down-to-earth and it seems strange that this quality should have made her the subject of derision from certain corners of the literary world, the sort who like to dismiss the elegant 69-year-old as “Queen of the Aga Saga” and her explorations of family dynamics and domestic life as “women’s writing”.

It would seem the combination of being a Cotswolds-born, Oxford-educated rector’s daughter and managing to shift stacks of novels to a devoted readership is a little too much for some critics.

“I feel that all snobberies and prejudices arise from fear and that makes one able to feel more kindly about it all. But I do wonder what these judges are afraid of. Do they think if people read my books they won’t read theirs?”

Still, she takes less notice of such things these days.

“It’s one of the very peaceful things about getting older, you know. There are things that would have hit me acutely a few years ago that I really don’t mind any more.”

She thinks instead of her readers; she remains terrified of letting down the people who snap up her books in their thousands.

While it would be “neurotically self indulgent”not to take some degree of pride in her past success (after all, three-quarters of a million people can’t be wrong), that only makes the weight of responsibility heavier when approaching a new project.

It’s partly the reason Trollope – whose modern-day reworking of Jane Austen’s Sense And Sensibility is due out next month – takes a method actor’s approach to research. For her most recent novel, The Soldier’s Wife, she went to live for a time on an army barracks, and in the past she has worked on a supermarket till and spent time in a women’s refuge.

"I have to confirm my suspicion of how it would feel to be in a particular situation,” she explains.

“My readers live the lives I write about and know far more about these areas than I do, so it behoves me to get it right for them.”

But that doesn’t make the business of getting words on to paper any easier. To her dismay, writing has become harder rather than easier as the years have gone on and every time she begins a new novel she frets that she won’t be able to pull it off.

“I always wonder about writers who say they can’t wait to get to their desks.

I’m much more likely to find an urgent errand that needs doing first. It’s a strange thing in that you’re faced with yourself with no intervening medium.

There’s no paint or piano.”

But she concludes that this discomfort is probably a good thing. “I think vulnerability and humility are a crucial part of being a reasonable writer. You have to doubt because that’s what makes you try harder. It makes me rather dread writing but it’s something I have to do.”

Trollope began writing aged 24 when pregnant with her first daughter Louise. The decision had nothing to do with chasing celebrity – “The term hadn’t been invented then! It was more a desire to communicate and connect.”

But it wasn’t until 1978, when she was in her mid-30s, that her first historical novel was published. It would be another 14 years before she found the publishing success she has enjoyed ever since with The Rector’s Wife, the number one bestseller in the summer of 1991.

Now she maintains that no one should start writing seriously until they are “at least” 35 years old. “You need to have been knocked about a bit by life to write fiction. It’s no bad thing to have had your heart broken or to have been made redundant or to have had a baby. Writers can lead quite rarefied lives but going through any of these life-changing things… it dumps you on the Northern Line in rush hour with everyone else.”

I wonder if she thinks marriage is best entered into later in life as well? She married her first husband David Potter at the tender age of 22 and split up from him 18 years later. She divorced her second husband, the screenwriter Ian Curteis, in 2001.

“Perhaps I’m not the person to ask about that,” she says sadly. “I’m mad about family but I just don’t think I’m someone to pontificate about marriage. I’ve got a lot of relationships right – many with men – but not marriage, and I haven’t got to a point yet when I know how much of it was me and how much was not making the right choice.

I wouldn’t want to blame anyone.”

Would she marry again?

“No, no, no!

Things are absolutely lovely as they are.”

She is happy being “singlish" in her beloved London, where she relocated after years in the Cotswolds. She loves the bustle of the capital and its ceaseless potential for new material; Trollope is a shameless eavesdropper and gets many of her ideas from overheard conversations. “A lot of my life is spent on the edge of a room taking notes.”

Still, she sighs with pleasure at the thought of heading into the Sussex countryside for her forthcoming appearance at Charleston’s Small Wonder short story festival.

“I’m so in favour of the festival. Short stories are marvellous and sometimes overlooked – yet the good ones are like little unexploded bombs.”

But we shouldn’t anticipate any bite-sized Trollopes any time soon. She is not a novelist by accident. “I’m quite good,” she says with a wise laugh, “at knowing what I can do and what I can’t.”

* Joanna Trollope is at Small Wonder at Charleston on Sunday, September 29. Visit charleston.org.uk.