Lily James hasn't been asked to star in the forthcoming 'Downton Abbey' movie

Speaking to PEOPLE.com, she said: "My character Rose moved off to New York, so it would be farfetched to bring her back. I would have loved to have come back for a scene, but for a movie, it can't be like a Christmas special and it needs to be a focused storyline. There was simply no space for Rose."

But Lily - who played Rose on the show from 2010 until 2015 - has had "months" to get her head around the fact she won't be joining her cast mates and is "so excited" to see her friends Laura Carmichael and Michelle Dockery reprise their roles.

She explained: "I spoke to Laura not long ago and was texting Michelle about Love Island and it's going to be really exciting. And the whole gang is coming back."

Filming for the movie is scheduled to kick off later this summer - three years after it left the small screen following a five-year successful run - ready for a 2019 release.

Producer Gareth Neame said: "When the television series drew to a close it was our dream to bring the millions of global fans a movie and now, after getting many stars aligned, we are shortly to go into production. Julian's [Fellowes] script charms, thrills and entertains, and in Brian Percival's hands we aim to deliver everything that one would hope for as 'Downton' comes to the big screen."

Joanne Froggatt - who played Anna Smith in the period drama - was one of the first of the original cast to comment on the news as she tweeted: "Delighted to announce we're getting the band back together! #DowntonMovie #DowntonAbbey (sic)"

Rumours about a movie have been rife for some time but the show's creator Julian created a storm of excitement last year when he said he had written a script for the blockbuster and was awaiting the go ahead from the studio.

He said at the time: "I've done some work on the script because I don't want to find there's a green light and no script ready.

"But we're still waiting for that green light from the studio. Then the biggest difficulty will be rounding up all the cast as, compared with most series, it has such a large cast. And it needs them to feel Downtonesque."