Thandie Newton and rapper Ludacris have joined the cast of Guy Ritchie's new gangster film 'Rockn Rolla'.The movie - about British gangsters who get involved with the Russian mob -began shooting in London earlier this month. It will also star '300' star Gerard Butler as a crafty but shady businessman and 'Eternal Sunshine of the Spotless Mind' actor Tom Wilkinson, whose character is one of London's main old-school gangsters who finds himself quitting crime because of foreign mobsters.Newton will play Butler's love interest - an accountant linked to the criminal underworld - while Ludacris is cast as an American musician trying to make it big in London.Ritchie has written the script for the film, which will cost about 10m to make - a low budget by Hollywood standards.The British film maker's wife, Madonna, is also rumored to be appearing in the movie.