LADY Fiona Carnarvon was nowhere to be found when it came to our interview.

The switchboard were at a loss as to where in Highclere Castle she was, ditto her PA.

“We are trying to locate the countess now,” they said.

Ten minutes later, and rather breathless, she appeared.

She’d lost her labrador and had only just found him by the bins, where the remains of the Help For Heroes fundraising day tea had been tantalisingly disposed of.

“I’m quite exhausted,” she says, “but it was all for a good cause and it was an amazing day. I wanted to share Highclere with everyone and make sure they had a lovely day out, rather than holding some elitist black tie dinner.”

Which says it all really, because despite her privileged background, there is nothing high-and-mighty about Lady C.

She may be cashing in on Downton Abbey’s success, filmed at her husband’s ancestral home in Berkshire, but only to ensure Highclere’s survival for future generations.

“We all hoped it would be a success but the mania is quite extraordinary,” she says thoughtfully. “So 9pm every Sunday night is great PR and we are just trying to retain it.”

As soon as the ITV drama’s success first became apparent, Lady C locked herself in her study and began writing a book about the original Lady Almina, who turned Highclere into a hospital during WW1, and for whom Lady C has untold admiration.

“Lady Almina was an amazing woman. And most of the historical books on Highclere have been about the family’s dukes and earls so it was amazing to be able to write about a woman. She was an real example of how you just get on with it, as her patients testified.”

So quite similar to Downton, right, then? “Quite different,” Lady C says firmly. “This was a proper hospital not a convalescent home, so it was monstrously different. And Lady Almina took all the patients in and made sure they felt special and rested, away from the horrors of the front and the field hospital beds. She was utterly focused on her patients.”

And what of Lady Almina’s marriage? “It was strategic to marry someone with money, but he absolutely fell in love with her too.”

So did Lady C find any glaring similarities between their two lives. “On, no,” she says in modest horror. “The house is still here and long may it continue but I’m not saving lives like she did, although there are some parallels I suppose.

“I have the courage to make things happen when I think it’s the right thing to do and one of the most important things is always to act with courage and kindness, thank people for all they do because they don’t have to, whether they are paid or volunteers, and have respect for others, which I carry at the forefront of my mind. So we are singing from the same hymn sheet because there’s no point doing it if you don’t do it properly.”

And yet Lady C admits she had no idea what she was taking on when she married the Earl. “No,” she laughs. “I just married a lovely, kind man and we loved each other, it was as simple as that. So we have always faced the challenges together.”

As for any preconceptions of their life, anyone who saw the Real Downton Abbey documentary will be under no illusions as to how hard it is to keep such a mammoth stately home up-and-running.

“Yes there’s lots of multi-tasking going on,” Lady C acknowledges. “I think people are pretty clear now that we work hard and the publicity has only clarified that.

“God doesn’t give you a crystal ball so we just keep on reinvesting and repairing, instead of spending it on dresses, and pay for everything out of our revenue so we don’t have a deficit. It’s just housekeeping really.

“And we don’t go out much because although we do our bit for charity when we can, and it’s always nice to have supper out with friends, kitchen suppers to me are glorious and bed by 9pm,” she laughs. “But we also acknowledge that we are very lucky and just try to sustain that.”

So while Lady C does have housekeepers, cleaners, a castle manager, gardeners etc, they are all peddling frantically to keep Highclere afloat and have a common goal. “We have a committed team here,” she confirms.

“And writing the book was just another way to sustain the house and its history, because so many stately homes were knocked down after WW2, so we are just trying to make ours relevant so that people want to see it.”

Even so, 70,000 words is no mean feat, let alone the accompanying book tour. “In terms of public speaking sometimes I do get waves of panic,” Lady C admits, showing a vulnerable side for the first time. “And I wonder what on earth I’m doing. But then I remind myself my father was a Major General which is much more impressive, so I just get on with it.”

Lady Carnarvon will be talking at The Theatre, Chipping Norton on Monday at 7.45pm about her book Lady Almina and the Real Downton Abbey. Call 01608 642350 or see chippingnortontheatre.com