Prince William felt like an earthquake had smashed through his life when his mother died.

The 35-year-old royal was 15 years old when he lost Princess Diana in 1997, and the Duke of Cambridge has admitted there is "nothing like it in the world" than losing his parent.

Speaking about the loss in the documentary 'Diana, Our Mother: Her Life and Legacy', he said: "There's nothing like it in the world. There really isn't. It's like an earthquake has just run through the house and through your life and everything. Your mind is completely split."

And William - who has four-year-old son Prince George and two-year-old daughter Princess Charlotte with his wife the Duchess of Cambridge - has admitted it took a long time for reality to sink in.

He added: "And it took me a while for it to actually sink in."

But William has "slowly" tried to "rebuild" his life over the past 20 years and talk about his grief to help him come to terms with the situation.

He explained: "The family came together and Harry and I tried to talk as best we could about it. But being so small at that age, it was very difficult to communicate or understand your feelings.It's very complicated.

"Slowly, you try and rebuild your life, and you try and understand what's happened."

William has revealed the thought of his late mother and what she would have wanted for her brood has helped him to cope.

He said: "I kept saying to myself that, you know, my mother would not want me to be upset. She'd not want me to be down. She'd not want me to be like this. I kept myself busy as well--which is good and bad sometimes--but allows you to kind of get through that initial shock phase."