Kristen Stewart thinks Princess Diana was the "most isolated human".

The 31-year-old actress stars as the late Princess in 'Spencer' - a new psychological drama film that focuses on her decision to split from Prince Charles - and Kristen explained that while Diana was warm and generous towards other people, she also felt "isolated and lonely".

The Hollywood star told The Sun on Sunday newspaper: "She was born with the power to help other people. There are some people that are endowed with an undeniable, penetrating energy. And all she wanted was to just have it back.

"Ironically, she was the most unknowable person and somebody who really never wanted to be alone. Some people are good at it, some people hate it.

"She wanted connection, she wanted people in her life and she was the most isolated human, at least over the imagining of these three days. We wanted that to come to a head."

Meanwhile, Pablo Larraín, the film's director, admitted 'Spencer' might not be an easy watch for Princes William and Harry.

Despite this, Pablo insisted he has "enormous respect" for the royals.

The filmmaker - who previously helmed a movie about former US First Lady Jackie Kennedy - said: "If they want to see it, we are eventually going to connect with someone that could get it to them.

"I have enormous respect for them and I have a lot of admiration for what Harry has done. But this could be a situation that is not easy for them.

"I wouldn’t want to do anything that would just create any kind of problems. They’ve had enough."