ITV News Arts Editor Nina Nannar asked the cast why they believe the period drama, written by Julian Fellowes, is such a roaring success.
"It's an escape into a different world, and the world we live in is quite a stressful, anxious place...people need to escape into different worlds," Elizabeth McGovern, who plays the Countess of Grantham, said.
While new cast member Tuppence Middleton, Lucy Smith in the film, says the appeal comes from the "quintessential Britishness of it."
"I think as Brits we watch it and there's something about the history that really appeals to us, but also globally, it's just so British," she said.
The successful ITV period drama first landed on our screens in 2010 and ran for six series, spanning five years, and captivated a British and worldwide audience.
Four years have passed since Downton was last on our screens, making the movie adaptation highly anticipated.
Downton Abbey followed the aristocratic Crawley family as they navigate the post-Edwardian era, all set in their stately home.
But what made the TV series so unique is it followed the lives of those living upstairs and downstairs, the aristocrats and the servants who serve them everyday.
The big-screen plot centres on a royal visit by King George V and Queen Mary to the country estate of Downton.
The cast members say the film was really made for the fans, as demand never wavered.
"What gave everybody confidence was the demand for the film never abated," Carter said.
"Every time we met a fan on the street, 'is there going to be a film,' 'when's there going to be a film' and I think that was the driver of getting it made."
McGovern added: "The film is for them, I mean that was the idea, let's do it for these people who have become attached to these characters and let's shoot them in a very loving way, because we have this history together.
"Us and our audience, and so it was everybody's intention to please them, not to please ourselves."
While McGovern said the film dispels the Hollywood myth that women are not interesting beyond a certain age.
Dame Maggie Smith reprises her role as the sharp-tongued Dowagess Countess, alongside Geraldine James's, who plays Queen Mary and Penelope Wilton's Isobel Crawley.
"People do engage with older women characters, almost as much as they do the younger ones," McGovern said.
"Who doesn't love the Dowagess Countess, so it really flies in the face of this myth that Hollywood, over and over again promulgates, which is that women aren't interesting after age 30.
"Because they really are."
The film is set for release in the UK on Friday September 13.