AS THE ancestral seat of a succession of illustrious families, Great Tew Park is no stranger to aristocratic goings-on. So it is only fitting the manor’s grounds should play host to one of our most famous toffs.

Joining the great and good on the pristine lawns of the West Oxfordshire stately home this weekend will be Cora Crawley, the Countess of Grantham... and the Lady of Downton Abbey.

Okay, so her role as the long-suffering nouveau riche heiress may be pure fiction, but actress Elizabeth McGovern has another string to her bow.

When not gracing the set of Downton, she can be found fronting her own rock band, Sadie & the Hotheads – among the highlights at this weekend’s Cornbury festival.

And while millions still associate Elizabeth with the globally successful drama, she is determined not to let the show overshadow her musical sideline — even though, she confesses, the prospect of facing a live audience still scares her to death.

“I don’t have any method except to embrace the terror,” she says. “That’s the only thing I can think of that I do. I throw myself into it, somewhat like the footage of that guy skydiving from space.

"That correlates to me with that initial walk up to the microphone to get into that first song, putting your arms around that feeling of terror. It’s got easier for me as I’ve done more gigs. So hopefully it will be less and less scary as time goes on.”

Yet, despite the fear, she relishes the chance to get out of character — or, rather, assume a different one — that of the freewheeling rock star alongside like minded music-lovers.

“We’ve known each other for a decade,” she says. “But I suppose we officially became a band when the name came into my head in 2006 while sitting in a cafe having coffee with my husband [British film director Simon Curtis].

“I wrote on a napkin: ‘Sadie and the Hotheads’. I still have the napkin in my desk drawer.”

The idea led to tours, an album called How Not To Lose Things, and festivals.

Her Cornbury date, this Saturday, sees her share the bill with an eclectic bunch, including Keane, Echo & the Bunnymen, The Proclaimers, Lawson, James Arthur, Jack Savoretti, Osibisa and Tanita Tikaram.

Elizabeth describes her music as “whimsical, fun and warm”, but other than that, admits the brief is wide open. “It’s very hard to categorise,” she says. “That’s something I like about it.

“We gave ourselves a brief that we wanted to realise the lyrics of every song in the way they wanted to be realised so if it wanted to be jazzy, we’d go that way, and if it wanted to be something else, we went that way.

"In some ways I get frustrated, because I feel my singing voice is limited, but then it keeps the thing tied together because there’s only so much you can do. So for that, I’m grateful.”

Fans of the ITV1 series will be delighted to hear her on-screen daughter Lady Mary Crawley (Michelle Dockery) on one track of the album. She has also been known to join her on stage. Elizabeth said the pair had found a “special connection” through their love of music.

“There were the days when we would always run back to my trailer to hike up our skirts and play songs,” she laughs. “We don’t do so much of that now — it’s difficult because in the last season we weren’t thrown together in scenes as much as we were, so we sort of got out of the habit of it.”

And how have the fans reacted to Sadie? “I think that remains to be seen,” she smiles.

“The hope is that they’ll get a kick out of it because I think that a lot of what my music is about is being a parent and being a mother, which of course is very much what the part of Cora is about. I don’t think that’s different, really, whether you’re in 1918 or 2013. So I hope people who like Downton Abbey and my character can embrace the music as well.”

As an honorary Brit, does she find herself missing America?

“I don’t as much as I used to, because I’ve been here so long now. I like going back there, though. I miss the people.

“I feel there’s a rhythm to the way they operate that will always be my rhythm. But I feel definitely my home is the UK after all these years.

“In fact, if there’s anybody who would ever want to move to America, it would probably be my English husband — and not me.”

Does she think Sadie will outlive Cora, or is Downton here to stay?

“I don’t know,” she says. “I think everybody wants to be careful that it doesn’t outstay its welcome. But it seems to be something people really like, so I think they want to continue as long as it makes sense.”