Production of an Downton Abbey film is set to begin in 2018, three years after the series finale.

According to NBC Studios president Michael Edelstein, the project has been in the works "for some time" - but it is taking time to get original cast members on board.

He said: "We are working on getting the script right and then we've got to figure out how to get the cast together.

"Because as you know, people go on and do other things. But we're hopeful to make a movie sometime next year."

The comments came at the Singapore exhibition of the show, where cast members and producers came together to share costumes, sets and never-before-seen footage.

Sophie McShera, who played assistant cook Daisy Mason, said: "Oh, well, you've got confirmation before us. We have no idea if that's happening.

"But we would all love to be part of the film if it was to happen, for sure."

Laura Carmichael, who played Lady Edith Crawley, said she was "still waiting" to hear from producers.

"Well, tell my agent, because we're still waiting to know. We're hoping that will happen soon," she said.

Downton Abbey, which aired in more than 50 countries, portrays the lives of the aristocratic Crawley family and their servants against the backdrop of World War I. The series ended in 2015.

Emmy-winning writer and creator Julian Fellowes also said he hoped a film would be made.

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

"But we're still waiting for that green light from the studio. Then the biggest difficulty will be rounding up all the cast. And it needs them to feel Downtonesque," he added.

"I think we've got a film in us. I hope it happens."