Ledger was upbeat on 'Batman' set

Heath Ledger showed no signs of being troubled on the set of Batman movie The Dark Knight.

Gary Oldman, who plays Lt. Jim Gordon in the film, rubbished suggestions that the actor became obsessed with his role as the villainous Joker before his death.

"Because he died people want a dark story [that] he was so obsessed with the character, he was so contaminated by the Joker and he couldn't sleep and all of that stuff," Oldman told People.com.

"[But] in between takes he would sit on the kerbside and smoke a cigarette and laugh and talk about his daughter Matilda. I thought he was just a beautiful kid. I thought he was just wonderful. I had a real affection for him."

The 28-year-old star was found dead in January following an accidental overdose.

The Dark Knight will be released later this month.