Dame Helen Mirren joins prequel to Monsters Inc.

Dame Helen Mirren has joined the cast of Monsters University, Pixar's prequel to Monsters, Inc.

The Oscar-winning actress voices a dragon called Dean Hardscrabble, the headmistress of the movie's title institution.

Mirren has called herself "a great fan" of Pixar and said she was "honoured and exhilarated" to be taking part.

Monsters, Inc. was originally released in 2001 and made more than £355 million worldwide.

The prequel focuses on the relationship between main characters Mike and Sulley, played by Billy Crystal and John Goodman, when they met at university.

Mirren previously lent her voice to an animation when she appeared in 2010's Legend of the Guardians: The Owls of Ga'Hoole.

In 2007, she won an Oscar for her role as Queen Elizabeth II in Stephen Frears' The Queen.

Pixar's last theatrical release, Brave, won Best Animated Film at the 2013 Baftas but it received lukewarm reviews compared to earlier releases such as Toy Story, Up or Wall-E.

Monsters University is released in UK cinemas in July 2013.