With Ewan McGregor committed to play all four leading roles in his next movie, Scottish actor-turned-auteur Peter Capaldi may finally be ready to deliver on the promise that won him an Oscar in 1995 for his short “Franz Kafka’s It’s a Wonderful Life.”

Capaldi has taken a couple of wrong turns since then — into a development deal with Miramax that led nowhere, and a production deal with DNA Films for his ill-fated feature debut “Strictly Sinatra.”

But he has re-emerged with a hot screenplay, a better understanding of the way the industry works and a renewed determination not to compromise his own singular talent.

His latest project, currently untitled, is scheduled to shoot early in 2006, once McGregor has completed his six-month run in the West End revival of “Guys and Dolls.”

It’s a period film within a period film, and a comic double take on the classic tale of the prince and the pauper.

In Capaldi’s multilayered script, a couple of ambitious British producers in the 1930s are mounting an epic about the Jacobite rebellion of the 18th century, in which the Scottish forces of Bonnie Prince Charlie tried to overthrow the English king.

Hollywood playboy Leslie Grangely (McGregor) is hired to play the dual role of the prince and the double he uses to confuse his enemies. But when the star goes missing, the producers trick a look-alike extra (also McGregor) to fill Grangely’s shoes. The 1930s action interweaves with the story of Bonnie Prince Charlie.

Capaldi insists the story is not as complicated as it sounds, although he acknowledges it will take an actor of McGregor’s skill to pull it off. At one point, McGregor will be playing a 1930s amateur impersonating a star playing an 18th-century double impersonating a prince.

“You need someone who’s got the chops to deliver those different roles and delineate between them,” Capaldi says. “Ewan is perfect for it.”

Capaldi, a Scot of Italian extraction, studied as an illustrator before falling into acting via a role in “Local Hero.” He has carved himself a healthy TV, film and stage career specializing in comic, articulate, nervy characters, seemingly close to his own personality.

“I never really think of acting and directing as being separate, they are just different expressions of the same thing,” he says. “When I was acting, I was always asking abut the mechanics of filmmaking. I decided I would learn what everyone on set was doing, so I would feel less threatened.”

His first screenplay, the 1992 road movie “Soft Top, Hard Shoulder,” was produced by Richard Holmes, who also will produce the upcoming pic.

When Capaldi’s surreal short won an Oscar, the world seemed to lie at his feet. But as is so often true for hot young British talent, the path ahead wasn’t clearly marked.

“I don’t think I’m interested in making the kind of film that people in England are interested in,” he says. “There’s a lack of imagination and daring at the development level here. You tend to get an endless stream of films essentially rooted in the only reality executives seem to recognize, either the working-class milieu or the world of the last film that was successful.”

“Strictly Sinatra,” an uneven Scottish gangster drama, was his attempt to fit into this British scene after a fruitless year at Miramax, but the movie never quite gelled. “I am very grateful to DNA for giving me a chance,” he says. “But I compromised myself very early on, and afterwards I couldn’t get arrested as a filmmaker.”

He has spent the past four years, between acting jobs, working quietly on his latest screenplay with his wife, BBC script editor Elaine Collins. “The biggest thing I have realized was that you have to choose your collaborators very carefully, and that not everybody can like you,” he says. “The process of filmmaking is so difficult, there’s no point in doing it unless you can do it the way you want.”