It's been over 21 years since Princess Diana's tragically passed away.
While Prince William - and his brother Prince Harry - continue to melt hearts around the world with their touching tributes to the late Princess, the 36-year-old admits he's still "very angry" about her death and finds "it very difficult to talk about."
But the Duke of Cambridge's most heart-wrenching revelation following her death, is a promise he made to his mother when we was just 14-years-old.
When Princess Diana and Prince Charles divorced, there was a massive debate around whether the people's Princess should retain her title.
While the Queen was happy for her to keep it, Charles was not.
Which meant Diana ultimately had her 'Her Royal Highness' title stripped away.
In losing her title, Diana was required to curtsey to her sons - which upset a young Prince William greatly.
So he vowed to help his mum reclaim her title.
The then 14-year-old reportedly said: "Don't worry Mummy, I will give it back to you one day when I am king."
Unfortunately Prince William never had the chance to fulfil his promise as three years later, his mother died in Paris.
We're not crying! You're not crying!