Prince Harry has revealed he sought counselling after two years of “total chaos” after spending nearly 20 years of “not thinking” about the death of his mother.

Prince Harry was 12 when Princess Diana was killed in a car crash, but he said it was not until his late 20s that he processed the grief.

The 32-year-old has told Britain’s Daily Telegraph newspaper he tried to block out the pain.

“My way of dealing with it was sticking my head in the sand, refusing to ever think about my mum, because why would that help?

“(I thought) it’s only going to make you sad, it’s not going to bring her back. So from an emotional side, I was like ‘right, don’t ever let your emotions be part of anything’.

“So I was a typical 20, 25, 28-year-old running around going ‘life is great’, or ‘life is fine’ and that was exactly it.

“And then (I) started to have a few conversations and actually all of a sudden, all of this grief that I have never processed started to come to the forefront and I was like, there is actually a lot of stuff here that I need to deal with.”

Princess Diana with young princes William and Harry in 1987. Photo: AAP

He said he shut down his emotions after her death which had “a quite serious effect on, not only my personal life, but my work as well”.

The prince sought help after Prince William advised him that he had to deal with the grief.

Prince Harry said coping with the death of his mother while in the public eye had led him to coming “very close to a complete breakdown on numerous occasions”.

He said boxing “saved” him after he took it up to deal with his aggression, after nearly “punching someone” when he was 28.

Asked whether he had ever been to see a “shrink”, he replied: “I’ve done that a couple of times, more than a couple of times, but it’s great.”

“I know there’s huge merit in talking about your issues and the only thing about keeping it quiet, it’s only ever going to make it worse – not just for you but everybody else around you as well – because you become a problem and I, through a lot of my 20s, was a problem and I didn’t know how to deal with it.”

The Prince, who recently went public with his relationship with US actress Meghan Markle, said that he was now in a “good place”.

“Because of the process I have been through over the past two and a half years, I’ve now been able to take my work seriously, been able to take my private life seriously as well, and been able to put blood, sweat and tears into the things that really make a difference and things that I think will make a difference to everybody else.”

British Prime Minister Theresa May praised Prince Harry for his decision to speak out, saying it would help “smash the stigma around mental health”.

“Mental health problems affect people of all ages and all backgrounds,” May said.

“The bravery of those in public positions who speak out about their experiences helps smash the stigma around mental health and will help thousands of people to realise they are not alone.”