London: "King Kong" actress Naomi Watts reveals that she regularly wept while filming the biopic "Diana" because the Royal's life seemed very tragic. The 44-year-old actress, who plays Diana in the movie, constantly felt emotional on the sets, reported Daily Star. "It was an emotional one to do, definitely. There were loads of tears on set, tons of them, because it's a tragic story," Watts said. "It's hard for anyone to come out of a divorce well, particularly when you're under such scrutiny. And then she was sadly gone," she added. Watts initially refused to do the role over concerns that the biopic would upset the royal family. "Diana" shows the last two years of the princess's life before she was killed in a car crash in 1997. It also follows her relationship with surgeon Hasnat Khan, played by Naveen Andrews, 44.