Prince William choked back tears as he discussed the devastating impact of suicide with a woman whose husband took his own life in a short film released by the British royal's office on Friday to mark World Mental Health Day.

In the film, the heir to the throne speaks with Rhian Mannings, whose husband Paul took his life five days after the sudden death of their young son George from illness in 2012, at her home in Cardiff.

They discuss the need for better support for those who are bereaved or affected by suicide.

He becomes clearly emotional after asking Mannings, who founded bereavement charity 2wish to help those who experienced the unexpected death of a child or a young adult, what she would have said to her husband.

'ARE YOU OK?'

"I would just like to sit him down like this and just say, 'Why didn't you come to me?' Because he's missed out on just so much joy, and we would have been OK. And I think that's what the hardest thing is, we would have been OK," she told the prince, who then tries to hold back tears.

"Are you OK?" Mannings asks him.

"I'm sorry," William replies. "It’s just it’s hard to ask these questions that I…"

"No, it’s fine. It’s just you’ve got children ... It’s hard ... And you’ve experienced loss yourself."

Last year, William was among the mourners at the funeral of Thomas Kingston, the son-in-law of Prince Michael of Kent, the late Queen Elizabeth's cousin, who died by suicide after suffering from the adverse effects of medication.

The film was released to coincide with the launch of a National Suicide Prevention Network by the Royal Foundation, William and his wife Kate's charitable organisation, which will focus on understanding the causes of suicide and providing accessible support.

Every year in Britain, more than 7,000 deaths are caused by suicide, William's office said.