Prince William and Harry have described their mother, Princess Diana, as "one of the naughtiest parents", while recalling childhood memories for a new documentary to mark the 20th anniversary of her death.
The documentary, 'Diana, Our Mother: Her Life and Legacy', features William and Harry talking about her life behind closed doors and they pay tribute to the ways she shaped them.
Princess Diana died in a car accident on August 31, 1997.
Dodi Fayed, her lover and the driver Henri Pau also died in the crash.
"This is the first time that the two of us have ever spoken about her as a mother," Prince Harry says on the new promotional advertisement for the documentary that aired in the UK this morning.
"She was our mum. She still is our mum. And of course, as a son I would say this, she was the best mum in the world. She smothered us with love, that's for sure.
Prince William revealed Princess Diana was "very informal and really enjoyed the laughter and the fun...But she understood that there was a real life outside of Palace walls."
The trailer opened with a poignant scene showing Prince William holding a photo showing The Princess holding him whilst pregnant with Harry.
"Believe it or not, you and I are both in this photograph, you're in the tummy!," The Duke of Cambridge can be heard saying.
One of the people who commissioned the documentary for ITV, Jo Clinton-Davis, said the film "will offer viewers a fresh and revealing insight into Princess Diana through the personal and intimate reflections of her two sons and of her friends and family, many of whom have never spoken before, to bring together a definitive portrait of a unique person who touched the lives of millions."
Diana, Our Mother will be broadcast in Britain for the first time on Saturday night (local time).