In a wide-ranging interview with GQ magazine, one of his most candid to date, Britain's Prince William talked about how much his misses his late mother, Princess Diana.

"I would like to have had her advice. I would love her to have met Catherine and to have seen the children grow up. It makes me sad that she won't, that they will never know her, " the Duke of Cambridge told GQ writer Alastair Campbell.

The prince married Catherine, Duchess of Cambridge, in 2011 and the couple have two children, Prince George, three and Princess Charlotte , two.

Prince William appears on the GQ cover, which comes out a few months before the 20th anniversary of the Paris car crash that killed Princess Diana. Prince William was 15 while his brother Prince Harry was 12.

"It has taken me almost 20 years to get to that stage. I still find it difficult now because at the time it was so raw. And also it is not like most people's grief, because everyone else knows about it, everyone knows the story, everyone knows her."

He also talked extensively about mental health and Heads Together, a campaign he heads together with his wife and brother aimed at ending the stigma around mental illness.

"I've been really shocked how many people live in fear and in silence because of their mental illness. I just don't understand it. I know I come across as quite reserved and shy, I don't always have my emotions brewing, but behind closed doors I think about the issues, I get very passionate about things. I rely on people around me for opinions, and I am a great believer in communication on these issues."

The article also includes a candid shot of the prince and his family playing around in a garden. "I could not do my job without the stability of the family. Stability at home is so important to me. I want to bring up my children in a happy, stable, secure world and that is so important to both of us as parents," he said.