The royal family just released three photographs from Princess Diana's personal album

On the eve of a new HBO documentary, Diana, Our Mother: Her Life and Legacy, the Kensington Palace Twitter account has released three photos of Princess Diana.

The images show the late Princess of Wales with her sons Prince Harry and Prince William. This August will mark 20 years since her death in a traffic collision.

"The Duke and Prince Harry are pleased to share 3 photographs from the personal photo album of the late Diana, Princess of Wales," the tweet read.

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In clips from the documentary, both sons flip through a photo album discussing memories of the Diana as a mother. "Her 20th anniversary year feels like a good time to remember all the good things about her," Prince William said.

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The two also discuss their last conversations with their mother, and how they both regret the brevity of their final phone call.

"I can't necessarily remember what I said, but all I do remember is regretting for the rest of my life how short the phone call was," Prince Harry explained, according to CNN.

The full documentary will air on HBO on July 24 at 10 p.m. EST.