Imelda Staunton has joined the cast of the 'Downton Abbey' movie.

The 'Harry Potter' actress will appear alongside her husband Jim Carter - who plays butler Charles Carson in the popular TV series - in the motion picture, which has officially started production.

Geraldine James, Simon Jones, David Haig, Tuppence Middleton, Kate Phillips, and Stephen Campbell Moore have also been announced for the film, which will also feature the original cast of Michelle Dockery, Elizabeth McGovern, Dame Maggie Smith, and Hugh Bonneville.

Gareth Neame - who will produce the motion picture alongside creator Julian Fellowes, and Liz Trubridge - said: ''We are excited that photography is about to start on the long-awaited film and that the beloved main characters will be joined by such exceptional actors playing new roles unique to the movie.''

Brian Percival will executive produce the movie alongside Nigel Marchant, and Michael Engler will direct.

While plot details are yet to have been revealed, the film will tell the story of the fictional Crawley family and their servants who work for them in an English country home in the early 1900s.

However, Lily James - who played Lady Rose MacClare in the TV series from 2010 to 2015 - will not be returning for the motion picture.

She recently 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.''

Speculation about a 'Downton' movie had been rife for years after the fictional country estate closed its doors for what was thought to be the final time in December 2015 when the TV series came to an end.

But last month, a tweet on the official 'Downton Abbey' Twitter account read: ''Welcome back to Downton! We're thrilled to announce that #DowntonAbbey is coming to the big screen. Film production begins this summer.''

Joanne Froggatt - who played Anna Smith in the period drama - was one of the first of the original cast to comment on the news about the film.

She tweeted: ''Delighted to announce we're getting the band back together! #DowntonMovie #DowntonAbbey (sic)''