The Duke of Cambridge has revealed that responding to a traumatic incident when he worked for the air ambulance sent him "over the edge" and he was left feeling "very sad and very down".
Speaking at the This Can Happen conference on Tuesday, he said that becoming a father had further intensified the impact the job had on his mental health.
The inaugural event at London's O2, was aimed at tackling mental health in the workplace by getting people to open about issues that affect them in their job, no matter what position they hold within a company.
William, who along with his wife, the Duchess of Cambridge and his brother, Prince Harry, has been a passionate mental health campaigner, opened up about his own experiences while working as a pilot of the East Anglian air ambulance
He told the audience: "I worked several times on some very traumatic jobs involving children.
"After I had my own children I think the relation between the job and the personal life what really took me over the edge.
"And I started feeling things that I've never felt before and I got very sad and very down about this particular family.
"You start to take away bits of the job. And you take them home and you keep them in your body."
The prince did not go into details about the incident, but said he was lucky to have worked for the RAF and the East Anglian Air Ambulance, because of their good mental health working practices.
Speaking about his time with the air ambulance, he said: “Talking was really important, but even that wasn’t quite enough for one particular incident for me.
It is understood he was discussing an accident involving a child.
Talking to colleagues helped him to “come to terms with the enormous sadness” of what had happened, he added.
About 120 employers from different sectors were represented at the event, which was attended by roughly 750 people.
He urged employers to look after the mental health of workers.
While taking part in a panel discussion, William added: “We spend a vast amount of our time at work.
“There should be a much more open, supportive and compassionate working environment to deal with those sorts of problems.
“There’s still a stigma about mental health. We are chipping away at it but that wall needs to be smashed down.”
Workers need to feel they can speak to people in the HR department, he added.
He also spoke about the responsibility of looking after his own staff, who he said sometimes work “silly hours”.
It is important they “keep an eye on the hours they work” and the commuting they do, he added.
William campaigns alongside the Duchess of Cambridge and the Duke of Sussex for mental health initiative Heads Together.