Dan Stevens to play Lancelot in new Night at the Museum movie

Former Downton Abbey star Dan Stevens has joined the cast of the new Night At The Museum movie.

The Brit, who played Matthew Crawley on the period drama, will portray King Arthur's one-time sidekick Sir Lancelot in the third installment of Ben Stiller's hit film series.

Stiller and Robin Williams will return as security guard Larry Daley and Teddy Roosevelt, respectively, when the film starts shooting in February (14).