Colin Firth feared he would look old and decrepit playing Emma Stone's love interest in Woody Allen's new film Magic In The Moonlight, because of their 29-year age gap.

The King's Speech star, 54, plays an illusionist who sets out to unmask a bogus clairvoyant, portrayed by Stone, 25, in the comedy, and admits he feared the audience's reaction to his onscreen romance with The Amazing Spider-Man.

Firth tells The Independent, "I was very aware of it (age gap) at the beginning, when I found out who was playing the roles. At the time I thought, 'I'm going to seem so old and washed up next to Emma Stone!' I wasn't exactly relishing being on the unflattering end of that.

"Once we were underway, other things came to the fore. But people are going to draw attention to it. I get it. I really do understand. It's noticeable."

Many critics have made the point that Allen should have cast an older woman or a younger leading man, but the film is still a hit among many fans of the director.