Doctor Who star David Tennant and Girls Aloud singer Sarah Harding are joining the cast of the new St Trinian’s movie, it has been confirmed.

The pair will star alongside Rupert Everett and Colin Firth in St Trinian’s II: The Legend of Fritton’s Gold.

It follows the success of 2007’s St Trinian’s, which grossed £15 million at the UK box office.

A spokeswoman for the movie said Harding, 27, will play a ‘cool new schoolgirl’.

It is not her first stint on the big screen as Harding played a cameo role in the 2007 film, alongside her bandmates. She also has major role in a new BBC Two drama called Freefall.

Tennant, 38, whose role as The Doctor will be taken over by Matt Smith next year, will turn from hero to villain, playing a character called Pomfrey, who has sidekicks from a women-hating secret society.

Ashes to Ashes actress Montserrat Lombard is also joining the line-up.