The Duke of Cambridge has revealed the “life-changing” experience of having children brought back the emotions he felt following the death of his mother.

Speaking candidly in a new BBC documentary, William said if you live through a “traumatic” event, like losing a parent at a young age, those feelings can resurface during the amazing but scary period of parenthood.

The duke who has three children – Prince George, Princess Charlotte and Prince Louis – admitted he had found things “overwhelming” at times but he and wife Kate supported each other as they went through those “moments” together.

William’s comments will feature in A forthcoming film that examines men’s mental health through the prism of football, and during a discussion with former professional footballer Marvin Sordell, the ex-striker who said he struggled when he became a father for the first time a few years ago.

Sordell said “it was the hardest time in my life” and he found it difficult to be a role model to his child having grown up without a father. “I really struggled with my emotions at that time,” he added.

The former Bolton Wanderers player asked the duke, with fathers under so much “pressure” who he went to when he was “struggling”, and William replied: “Having children is the biggest life-changing moment, it really is.

“And I agree with you, I think when you’ve been through something traumatic in life – and that is like you say your dad not being around, my mother dying when I was younger – your emotions come back in leaps and bounds because it’s a very different phase of life.

“And there’s no one there to, kind of, help you, and I definitely found it very, at times, overwhelming.”

The duke added during the one-to-one chat with Sordell: “Me and Catherine particularly, we support each other and we go through those moments together and we kind of evolve and learn together.”

William was 15 and his brother Harry just 12 when their mother Diana, Princess of Wales was killed in a Paris car crash in 1997.

In a documentary released last year, that also dealt with mental health, the duke said that following his bereavement there was “pain like no other pain”.

In recent years William and his brother have talked extensively about how they dealt with their mother’s death as they promoted their Heads Together mental health campaign, that encourages people to talk about their problems or listen to others facing issues.

The duke told the ex-player: “But I do agree with you, I think emotionally things come out of the blue that you don’t ever expect or maybe you think you’ve dealt with and so I can completely relate to what you’re saying about children coming along, it’s one of the most amazing moments of life but it’s also one of the scariest.”

The documentary, which will be screened on Thursday, had access to the duke over the course of a year and features him meeting players, fans and managers from grassroots to the elite as part of his efforts to start the biggest ever conversation on mental health, through football.

William has also spearheaded the Heads Up initiative, a campaign which aims to raise awareness about mental health, spark conversations between football fans – particularly men – about the issue, and direct those in need towards support.

Football, Prince William And Our Mental Health will be broadcast on Thursday at 8.05pm on BBC One.