Prince Harry has said he regrets not opening up sooner about how his mother's death affected him.
The 31-year-old revealed he only began talking three years ago about the sudden death of Diana, Princess of Wales.
Harry was hosting a Kensington Palace event for mental health charity Heads Up, attended by sporting stars - such as Rio Ferdinand, Victoria Pendleton and Dame Kelly Holmes - who spoke about their psychological problems.
They were all accompanied by a partner, relative or sports psychologist who had helped them through their darkest moments.
The BBC reported that Ferdinand, whose wife died last year, asked Harry about the impact it might have on his children. Harry replied: "I really regret not ever talking about it," adding that he did not speak about losing his mother "for the first 28 years of my life".
Harry was 12 and his brother William 15 when Diana was killed in a car crash in Paris on August 31 1997.
He added: "It's OK to suffer, as long as you talk about it. It's not a weakness. Weakness is having a problem and not recognising it and not solving that problem."
Heads Together was founded by Harry and the Duke and Duchess of Cambridge and has brought together eight mental health charities and organisations to tackle the stigma around depression and other psychological problems.
Father-of-three Ferdinand, whose wife, Rebecca Ellison, died from cancer, said of the Prince: "He's gone through different stages in his life that my kids are going to be going towards. So to get some of his experiences is very rewarding for me and very educational in many ways."
Harry added: "The key message here today is that everyone can suffer from mental health.
"Whether you're a member of the Royal Family, whether you're a soldier, whether you're a sports star, whether you're a team sport, individual sport, whether you're a white van driver, whether you're a mother, father, a child, it doesn't really matter."