Princess Diana would have been the "best grandmother ever", her brother believes.

Princess Diana

Princess Diana

Earl Charles Spencer has opened up about his late sister - who tragically died in a car crash in Paris in 1997 aged 36 - admitting she was "quite naughty" as a kid but would've made the ideal role model for her son Prince William's children, George, four, and Charlotte, two.

Speaking on US documentary 'The Story of Diana' on ABC, on which he shared previously unseen videos of the royal as a youngster, he said: "You'd be wrong to think of Diana was a saintly child. She was quite naughty. Never with malice, you know, just sort of pushing the boundaries.

"One of the great tragedies of course is that Diana would have been the best grandmother ever."

The Princess of Wales' brother also admitted he is delighted to hear she is still well respected.

He said: "I love the fact that there's still such veneration inside her immediate family for what she was and what she meant and I think that's fantastic."

Charles recently admitted he felt as though he was "almost out of oxygen" when he delivered the eulogy at his sister's funeral.

He said: "She'd left me as guardian. I was looking directly at William and Harry across her coffin. In the final paragraph I had run out of energy, almost out of oxygen. I had to punch each syllable out of the base of my stomach."