Prince Harry, Prince William, and Catherine, Duchess of Cambridge, are set to appear in a BBC documentary about runners competing in the London Marathon.
The royal trio are the founders of the charity Heads Together - which has been named as the chosen charity for the Virgin London Marathon on April 23 - and will appear in a BBC documentary entitled 'Mind Over Marathon' later this month as they support 10 runners who are taking part in the race on behalf of their cause.
Heads Together is a charity which aims to end the stigma surrounding mental health, and the 10 runners featured in the documentary are all people who suffer with mental health problems themselves.
In a promotional video for the two-part documentary - which is set to air three days before the marathon on April 20 - 35-year-old Duchess Catherine can be heard telling the group: "You are all heroes."
The news of the documentary comes after Prince Harry, 32, recently released a video in which he said he, his 34-year-old brother William, and his sister-in-law Catherine would be cheering on the runners at the marathon.
He said in a lengthy speech: "You've been training for months and the start line to the 2017 Virgin Money London Marathon is finally within sight. I'm sure it will be one of the most rewarding experiences of your life.
"William, Katherine and I will be there to cheer you all on. We're really excited that Head's Together is the chosen charity for this year's marathon. We want to use this moment to end the stigma that stops people talking and change the conversation about mental health for good. You can make it the mental health marathon.
"We know that many of you will be running for some incredible charities because you have been directly affected by life-changing issues. You'll recognise the emotional impact these can have and how talking about it openly can help. We all have mental health just as we all have physical health, and you can all play your part in the biggest movement in mental health.
"Whatever cause you are running for, wear your vest with pride and please wear your Heads Together headband. When we work together we can achieve great things. Good luck, see you at the finish line."
'Mind Over Marathon' airs on BBC One on April 20, ahead of the Virgin London Marathon on April 23.