- Princess Diana was killed in a car crash in Paris in August 1997
- Prince William and Prince Harry are raising funds for a Diana statue
- Statue will be erected in London's Kensington Palace where she lived
"It was her speaking from Paris, I can't really necessarily remember what I said but all I do remember is probably regretting for the rest of my life how short the phone call was," Prince Harry told ITV for a documentary to commemorate their mother.
Prince William was just 15 and his brother Harry 12 when their mother and her boyfriend Dodi Al-Fayed were killed in August 1997 after the car they were in crashed in a tunnel in central Paris as it was being pursued at high speed by press photographers.
Their French chauffeur Henri Paul, who was later found to be over the legal blood alcohol limit, also died.
The two princes were in Balmoral, the queen's residence in the Scottish Highlands, and William had earlier told Diana of the "very good time" they were having.
"Harry and I were in a desperate rush to say goodbye, you know 'see you later'...if I'd known now obviously what was going to happen I wouldn't have been so blase about it and everything else," William told ITV.
To mark the 20th anniversary of her death, the princes announced earlier this year they were setting up a committee to raise funds to pay for a statue of Diana, who was known as the Princess of Wales.
The statue is to be erected in the public gardens of Kensington Palace in London, where she lived.
The documentary, entitled "Diana, Our mother: her Life and Legacy" is to be aired in the UK on Monday.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)