The third instalment in the hit family adventure series sees Ben Stiller's security guard Larry head from a museum in New York to work at London's British Museum.
Familiar faces Robin Williams, Ricky Gervais, Dick Van Dyke, Owen Wilson and Mickey Rooney (in his final film role) will return, with Downton Abbey's Dan Stevens a newcomer as Sir Lancelot.
Stevens will be taking part in a Twitter chat tomorrow (July 31) at 8pm BST through the Night at the Museum MuseumMovies feed. Fans can send in their questions through the hashtag #AskLancelot.
Night at the Museum: Secret of the Tomb will open in cinemas on December 19.