More than three years after Downton Abbey finished on ITV, a movie version is finally here. Laura Harding sits down with the show’s creator Julian Fellowes to find out more

Lord Julian Fellowes is seated at a table with an immaculate and rather large three-tiered cream cake in front of him, scattered with fresh strawberries and cloaked under a tall glass cloche.

“Is it a decoration or is it supposed to be eaten?” he muses.

It turns out he did not order the cake in the glamorous London hotel we are seated in, but somehow it has appeared in front of him, as sumptuous, delicious and decadent as his most successful creation.

That creation is, of course, the confection that is Downton Abbey, an opulent period drama about the Crawley family, their majestic home of the title, and the staff below stairs who keep it all running.

It ran for six series on ITV, concluding with a Christmas special in 2015. No sooner had the credits rolled that fans began clamouring for more, ideally on the big screen.

Now that wish has finally come true, with all the original cast, including Dame Maggie Smith, Michelle Dockery, Hugh Bonneville and Joanne Froggatt, and new additions including Imelda Staunton and Tuppence Middleton.

“I didn’t really believe there would be a film, to be perfectly honest,” 70-year-old Fellowes admits, “because I didn’t see it as inevitable.

“I was a big fan of Mad Men, I was a big fan of The West Wing, I was a big fan of The Good Wife - there were no films of any of those.

“So I didn’t see that just because it had been a big success as a series that a film was inevitable.

“But in the end the rumbling grew louder and finally it seemed there would be and then we had to get on and think what it was going to be about.”

What he settled on was a royal visit from King George V and Queen

Mary, which would send all residents of Downton into a tailspin.

“We wanted a central story that would involve everyone,” he says.

“There are lots of central stories that would have involved everyone but most of them are negative, most of them are epidemics and fires and disasters and I didn’t really want that. I wanted a positive central thing that would nevertheless involve everyone.”

“Even if they were anti- it, they would have a reaction to it.”

He stumbled on the idea of a royal visit while reading Black Diamonds, a book about the the Fitzwilliam family in Yorkshire.

“I was reading it and I thought, ‘Ooh, perhaps this is the answer - a tour of the county and they come to Downton for a night.’

The plotline is sure to go down a storm not only with fans of Downton and the royals at home, but also in the US, where the show has been a resounding triumph and has been showered with awards.

Its success there reflects that of Fellowes, who has always found his reception warmer on the other side of the pond than he has on home shores.

“America has been very good to me, there is no question about that,” he agrees. “I was an unfashionable type when I started writing and it’s no accident that it was an American, in the person of Robert Altman (the director who roped him in to write Gosford Park), that put me on the map because that wouldn’t have happened to me with the establishment in showbiz being what it is here.

“After I had won an Oscar (for that very screenplay), to a degree they were forced to reckon with me, but only to a degree. I was not what they wanted.

“And America has always been encouraging and welcoming and has - to say taken me seriously sounds a bit