Hip hop star Mos Def has landed the role of Ford Prefect in the new Hitchhikers Guide To The Galaxy movie.

And Zooey Deschanel has landed the role of Trillian, girlfriend of the three-armed, two-headed Zaphod Beeblebox - the only major role yet to be cast.

Robert Downey Jr had been approached over the role but, according to the Hollywood rumour mill, been ruled out because he wanted too many changes to the script.

The announcements follow the news that The Office's Martin Freeman is to play hero Arthur Dent, and Bill Nighy the mysterious Slartibartfast.

Filming starts at Estree Studios on April 19, with Garth Jennings of music video directors Hammer and Tongs at the helm.

Mos Def has previously appeared in Monster's Ball and the remake of The Italian Job, while Deschanel's credits include Elf and Almost Famous