"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," The Sun quoted Williams, as saying. "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," she added.
Following Williams, Naomi, who dated Ledger for two years, said of her ex flame: "His acting was just so touching, so connected in truth. I think he was just getting started." Philip Seymour Hoffman, Sean Penn and pal Ellen DeGeneres were among the other celebrities paid tribute to Ledger.