The Duke of Cambridge has praised the efforts of young people battling online bullying with a charity promoting the legacy of his mother Diana, Princess of Wales.

William said it was “heartbreaking” to hear how abuse over the internet had affected the lives of the teenage ambassadors from The Diana Award, when he spoke to the group to mark Anti-Bullying Week.

The Diana Award, set up in memory of the princess and her belief that young people have the power to change the world, has trained more than 35,000 young people as anti-bullying ambassadors working to help victims in schools and communities.

The duke surprised the young ambassadors by making an unannounced appearance on a video call to show his admiration for their work.

He heard how they endured online abuse themselves before deciding to use their experiences to support their peers.

William said: “It’s just horrible and it’s very moving to hear you guys talk about how you want to help others and make sure that doesn’t happen to anyone else.

“That is the most important thing, that you realise this isn’t going to beat you and you want to make sure that others are not going to go through the same torment that you guys have gone through.

“But I’m just so sorry that you’ve experienced these circumstances and these bullies. It’s heartbreaking to hear how much of an impact it’s had on your schooling, your life, and things like that.

“Clearly you guys have all taken this on and beaten it, which is fantastic. Because it can – and, sadly it does – get on top of too many people and some of them can’t come through it.”

Despite schools being closed for a large part of this year due to Covid-19, the charity’s anti-bullying ambassadors said abuse had just increasingly transferred online.

Rose Agnew, 14, from Warwick, Jude Bedford, 16, from Cambridge, Paige Keen, 14, from Norwich, and Isabel Broderick, 15, from the West Midlands, shared their experiences with the duke.

They were invited to join a video conversation on Thursday but had no idea it would be with the future king. “No way, no way,” Rose screamed in delight.

Laughing, William responded: “Well at least one of you recognised me. The other three are not quite sure…”

Isabel told him she had suffered social anxiety after being targeted by an anonymous online account that threatened to reveal fabricated personal and sensitive information about her at the end of Year 8.

She never found out who was responsible and it took her two years to even tell her mother.

William said: “That’s a lot for you to live with, that stress, that anxiety, that pressure. That’s horrible for you to have to live with that for so long.”

Paige was targeted by a group of boys who edited her online photos and called her “fat” or “ugly”, while Jude told of becoming fed up at being picked on.

Rose, who has been targeted by racism and other types of bullying and saw her school work badly affected, told William why she had become an ambassador.

“I joined the Diana Award and applied because I know what it’s like to be bullied and that’s a feeling that I want to try and prevent as many people from having as possible,” she said.

“When people hate you for a factor that you can’t control and that you can’t change, it just makes you feel so powerless.”

She told the duke there should be anti-bullying ambassadors in every school and having a peer-to-peer mentor when she was being targeted would have had a profound impact on her life.

When William asked if bullying had got worse due to lockdown and with everyone spending so much more time on video calls and social media before schools returned in September, Rose suggested it was worse when people were no longer face-to-face.

“What was being said generally when people were being bullied was a lot worse, as it had moved online, since our whole life had moved online and bullying went with it,” she said.