It has been more than 20 years since the tragic passing of Princess Diana, but her death continues to have an impact, as her son Prince William recently opened up about the grief he has felt.

“I think when you are bereaved at a very young age, anytime really, but particularly at a young age — I can resonate closely to that — you feel pain like no other pain,” the Duke of Cambridge, 36, told soccer pros during a discussion for BBC’s A Royal Team Talk: Tackling Mental Health, which will air on Sunday, May 19.

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“And you know that in your life it’s going to be very difficult to come across something that is going to be an even worse pain than that,” the royal continued. “But it also brings you so close to all those other people out there who have been bereaved.”

William also shared how important it is for him to be vulnerable, so that it may hopefully help others going through similar situations. “You instantly, when you talk to someone else, you can almost see it in their eyes sometimes. It’s a weird thing to say, but somebody — particularly me — someone who’s desperate to talk about bereavement, you can kind of pick up on it quite quickly,” the father-of-three explained.

“They want to talk about it. But they want you to go first, they want you to say, ‘It’s OK,’ they want to have your permission. In that particular conversation, one-on-one it’s OK to talk about bereavement,” he added.

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William wrapped it up by telling the athletes that it is completely fine to express yourself, despite of how one is conditioned. “I think particularly in Britain as well, we are nervous about our emotions. We are a bit embarrassed sometimes,” he said. “The British stiff upper lip thing, that’s great and we need to have that occasionally when times are really hard. There has to be a moment for that. But otherwise, we’ve got to relax a little bit and be able to talk about our emotions because we’re not robots.”

William’s mother died in August 1997 after being involved in a car crash. She was 36, while her eldest son was 15 at the time. Her other child, Prince Harry, was only 12. He has been greatly impacted as well, as on a recent trip to the Netherlands, he had a conversation with former soldier Dennis van der Stroon, and revealed how much he misses his mom.

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“I told Harry about my mother and we talked about our shared experience of missing a mom,” Dennis revealed, according to Hello! magazine. “He said missing a mother is like missing some kind of security, how you need that as a son and it falls away when you lose your mother. He said he meets a lot of people in his work who have lost a mother, father, sister, brother or relatives and when he hears their story, as he heard my story, he said he doesn’t feel so alone.”