Robert Downey Jr cuddled up to his heavily pregnant wife and promised he was not hanging up his superhero costume as his new drama opened the Toronto International Film Festival.

The Iron Man star laughed and hugged his producer wife Susan as their film The Judge debuted as the opening night gala of the prestigious festival.

The movie marks Robert's first role in a drama since The Soloist in 2009 and he admitted it was Susan who talked him into it as a contrast to comic book movies and comedies.

Speaking on the red carpet, he said: "I love doing those sorts of genre movies and I don't intend on retiring my jersey but she reminded me that I also did Chaplin and Less Than Zero and movies before and maybe I would like to do something like that again."

Robert stars opposite Robert Duvall, who plays the judge of the title, and he said everybody would be able to relate to the film. "If you have a family or you had a mom or dad or you have brothers or an old girlfriend or boyfriend and if you come from a big city or a small city you are probably going to like it."

Duvall added: "It's a very smart script, it's very smartly written with a lot of colours and contradiction and deep conclusions to be reached

"People always like courtroom dramas, that and Westerns, but this isn't a Western, it's a Midwestern."

Also at the premiere was a pregnant Kristen Bell, who was supporting her husband Dax Shepard, who also stars in the film.

Vera Farmiga, who plays an old flame of Robert's character, added some old-school glamour while Jeremy Strong, Ken Howard and Law And Order: Criminal Intent star Vincent D'Orofrio rounded out the cast.

The Toronto International Film Festival will run until September 13.