Robert Downey Jr. thinks the Iron Man 3 script is the "best" he has read.

The 46-year-old actor is set to reprise the role of businessman Tony Stark/Iron Man for the fourth time - following on from the character's appearance in ensemble comic book movie The Avengers - in the highly anticipated film, and he admits he is excited to get working on the Shane Black-directed feature.

Speaking at the UK premiere of new movie Sherlock Holmes: A Game of Shadows at the Empire Leicester Square, Robert told BANG Showbiz, "Iron Man 3? It's the best script I've read in five years. It's going to be a phenomenal theatre-going experience."

Filming on the movie is set to begin early next year ahead of a summer 2013 release.