Heath LedgerMichelle Williams, Naomi Watts and Philip Seymour Hoffman are amongst those paying tribute to Heath Ledger in this month’s Interview magazine, with many people referring to the actor’s boundless energy.

Michelle, Heath’s Brokeback Mountain co-star and the mother of his daughter Matilda, told the magazine: “He had an uncontrollable energy. He buzzed. He would jump out of bed. For as long as I’d known him, he had bouts with insomnia. He just had too much energy. His mind was turning, turning, turning - always turning.”

“He had a talent for everything that he put his mind to. He didn’t know limits.”

“I think that the interesting thing about Heath, which maybe people have only really fully discovered in his death, his how vulnerable he was. You can pick up on it in his performances, but it’s easy to overlook because he was so physical and beautiful and strong and masculine. But there was always that underlying sensitivity. That’s who he was.”

Philip Seymour Hoffman described the actor has having “childlike enthusiasm”, saying “his body was always in motion” while his agent Steve Alexander said he was a “rolling stone”.

Heath’s ex-girlfriend Naomi Watts though focused on his attacking, saying she feels “he was just getting started”: “His acting was just so touching, so connected in truth.”

Heath died of an accidental drug overdose in New York in January.