Three photographs of Princess Diana with her sons, which have never previously been made public, feature in a new promo for a documentary about her due to air on ITV.
The new images are taken from an album that Diana had collated which was only discovered in recent months by Prince Harry.
"Diana, Our Mother: Her Life and Legacy" will be shown on ITV later this month to celebrate the Princess of Wales' life and work in the 20th year since her death.
The promo shows the Duke of Cambridge and Prince Harry looking through photographs and talking about their mother.
"She was very informal and really enjoyed laughter and fun," the Duke of Cambridge is heard saying.
Speaking in the promo, Prince Harry says: "She was our mum, she still is our mum and as her son I would say this, she was the best mum in the world.
"She smothered us with love, that's for sure."
William was 15 and Harry just 12 when their mother was killed in a car crash in Paris on August 31, 1997.
- "Diana, Our Mother: Her Life and Legacy" will be shown on ITV in July
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