Aardman Animations, the UK animation house behind Chicken Run and DreamWorks SKG's upcoming Wallace & Gromit film, has finally caught its rat. Kate Winslet will play a savvy sewer rat called Rita in Flushed Away, rounding out the main cast on Aardman's next production.

Nicole Kidman had been amongst the actresses in talks for the part but Aardman confirmed yesterday that Winslet has been cast in the starring role opposite Hugh Jackman. Rita is a streetwise scavenger rat who meets Jackman's society rat after he is flushed out of his Kensington flat and into the sewer city of Ratropolis.

Rita helps him find his way home and, of course, save the city, despite the machinations of a vengeful toad played by Ian McKellen. Andy Serkis and, in another recent addition to the cast, Bill Nighy voice the villain's hench-rats.

Production will start imminently but will take place in Los Angeles, a first for the famously quirky Bristol company.

Aardman co-founders Peter Lord and David Sproxton decided to produce Flushed Away at DreamWorks' US studios as this is the company's first foray into CGI animation. While Aardman has a modest CGI arm for TV and commercials, the company's previous features have been in pioneering claymation.

"We simply are not scaled up for a full CGI feature", said Sproxton.

The company opted for CGI over claymation because of the amount of water in the film and the scope of the picture, which will depict the busy sewer city under London's streets. With the company's trademark animation characters Wallace and Gromit, human figures are only a full inches tall; here, the rats are roughly life-size.

"We managed to create a chicken farm [in Chicken Run]" said Lord. "But this time we are talking about an entire city."

The loss of the $40m feature will be a blow to the UK production sector, which is suffering from a weak dollar and was hit last week by the banning of so-called double dipping on its tax supports for filmmakers.

Aardman, however, has added some $40m to the total production volume this year, having produced another feature in the UK, animator and company partner Nick Park's big-screen debut with his Wallace and Gromit characters. Shooting on that project ends in April.

Flushed Away is expected to be ready for release in 2006, the year after Wallace & Gromit, as part of the company's five-picture deal with DreamWorks. Henry Anderson, David Bowers and Sam Fell are directing from a script by Dick Clement and Ian LaFrenais.