The 25-year-old actor - who is dating his `Twilight Saga`co-star off-screen - admitted Kristen looked "amazing" when her alter-ego Bella Swann turned into a blood-sucking "vampire queen" during the latest film in the franchise.

He said: "She was a sexy goddess. She looked amazing. It was funny because Bella is that girl that is always tripping on things, and then, she turns into this elegant woman, like a vampire queen.

"Kristen had the best twist in the plot!"

However, Robert - who plays vampire Edward Cullen in `Twilight` - admitted the couple`s on-screen sex scene was far from easy because there were so many crew members who wanted to have a say in how the pair`s intimacy panned out.

He added in an interview with Brazil`s Capricho magazine: "I was trying to do a sex scene and there was huge guy lying on the floor, looking at me and telling me what to do.

"The hardest thing was that, in normal movies, when you`re doing a sex scene, people don`t pressure you a lot because the director doesn`t want to intervene and suggest how he would do that.

"But in `Breaking Dawn` it was different, there was too much expectation. How to make all the people that were waiting for that moment happy."
sections: Celebrities