London, March 9 -- Pulp Fiction star Uma Thurman describes Robert Pattinson, her co-star in upcoming film "Bel Ami", as a "very serious" actor who is constantly working hard to bring his skills up to the next level.Uma is finding it very difficult to be as serious as the Hollywood heartthrob, who is essaying the role of a 19th century Parisienne womaniser Georges Duroy in the film, the Contactmusic.comreported."He's very serious. He did a huge amount of rehearsals in his own time. I think that's what you do when you're a young actor, when you take your work very seriously and want to take it to the next level," Thurman said.Talking about herself, she added, "When you've been doing this a really long time, it's hard to take it all so seriously. I said to him, 'Don't get too upset about it, because, before you knowit, Twilight will just be an old film that made you lucky enough to get another job. But when you're in that position and you're young, it's hard to hear through the noise".