Dame Maggie Smith has signed up to the forthcoming big screen adaption of 'Downton Abbey'.

Dame Maggie Smith

Dame Maggie Smith

The masterminds behind the popular series have been given the go-ahead to turn the period drama into a blockbuster, and producers have already secured their first cast member.

Speaking to the DailyMail.co.uk, Michael Fox - who portrayed Andy Parker in the series - confirmed that the 81-year-old actress will reprise her role as Violet Crawley.

He added to the publication: "She elevates it to something else, because she is such a legend and a national treasure.

"The film without her would still be good with all the other actors, but it puts a stamp of quality with her in it."

News that Maggie has agreed to appear in the movie version of the ITV series will no doubt come as a shock to fans as she admitted last year that she didn't think she'd be able to as Violet was "too old."

Asked whether she would appear in a movie version of the period drama, she said: "I can't - what age would she be?"

Viewers were thrown into mourning last Christmas when 'Downton...' came to a dramatic end following five years on screen but creator Julian Fellowes has always shared his burning desire to turn the drama into a film one day.

However, the 67-year-old director hinted that he was waiting on vital cast members - believed to be Hugh Bonneville and Michelle Dockery - to free up their schedules for filming.

He said recently: "Let's just say it's not me slowing things down. The difficulty is rounding up the actors. One is in America making a new series, another is in a play ... My lips are sealed! It's very unlikely there won't be a film because there is an audience out there for it. I do hope there is going to be a 'Downton Abbey' film. It's going to be fun once everything is sorted but we just need to restructure it."

It's believed filming for the movie will kick off next year.