The Duke of Cambridge has revealed he has been anonymously volunteering on a crisis helpline during lockdown.
He has been volunteering at Shout 85258, which offers support via text message to people in personal crisis.
Prince William said he had been answering messages after being trained by the mental health charity.
Last month he told fellow volunteers in a video call: "I'm going to share a little secret with you guys, but I'm actually on the platform volunteering."
Those texting the round-the-clock service would not know they are talking to a member of the Royal Family - like Shout's 2,000 volunteers, William would use a pseudonym on the platform.
Kensington Palace announced the prince's involvement to mark Volunteers Week, which ends on Sunday.
A new photograph of the duke with Prince George and Princess Charlotte volunteering on the Sandringham Estate, taken by the Duchess of Cambridge, has also been released.
The Queen has praised the work of volunteers in a special message, saying: "As Volunteers' Week draws to a close, it is inspiring to reflect on the many thousands of people, who through their acts of generosity and kindness, have achieved so much for the greater good.
"I have been following with interest how men and women from around the world, including my own family, have been helping and recognising the vital role of the volunteer.
"I send my best wishes to all those who give themselves so freely and selflessly in the service of others."
The Cambridges and the Duke and Duchess of Sussex helped to launch Shout 85258 last year - investing £3m in the service via their Royal Foundation.
In a little over a year since then, more than 300,000 text conversations have been had on the service.
Around 65% of those texting are aged under 25, the charity said, with many messengers seeking mental health support.
What do Shout volunteers do?
By BBC journalist and Shout volunteer Tony Smith
Training as a crisis volunteer at Shout puts William in the frontline of services for young people in distress - and it's a tough role.
CVs, as they're known, undertake special training to support those in crisis. On the Shout platform they'll encounter, and be tasked with helping, those in very real distress.
Some texters are experiencing depression or panic attacks, others are self-harming. A large proportion say they feel suicidal.
The job of the CV is to lead that texter to a cool, calm place where they may begin to establish solutions. Sometimes they'll just need to build resilience, with support from friends or family. In others, they'll be guided toward charities or NHS mental health support.
It's not unusual for a texter to be about to take his or her own life. This can lead to what Shout call an 'Active Rescue' - the CV will continue gently talking to the texter while the emergency services are called in by a supervisor.
Whether it be talking someone down from a bridge, or persuading them to put away that bottle of pills, these conversations can be gruelling and rewarding in equal measure. The fact that the second in line to the throne is now routinely helping people in such desperate situations is hugely significant - it gives Prince William a unique perspective on what young people in crisis may be going through.
Meanwhile, the Duchess of Cornwall, the Duchess of Cambridge, the Countess of Wessex and the Duchess of Gloucester have been calling people who are self-isolating or vulnerable, as part of the Royal Voluntary Service's NHS Volunteer Responders scheme.
The Countess of Wessex has also been privately volunteering to support efforts in local communities, including once a week with Mealforce and Helpforce, helping to provide daily meals for NHS workers across London.
More than 750,000 people signed up to be part of the scheme's "volunteer army" after it launched in April, but some later expressed frustration at not having been used.
Last week, the Duchess of Cambridge thanked others who had signed up to help the scheme, calling them "the backbone of our country".
She and Prince William marked Volunteers Week by holding video calls with those helping charities in England and Wales.
Among them were those working at Conscious Youth, which helps young people from mainly black and other ethnic minority backgrounds in West Yorkshire.
During the call, Prince William joked about home-schooling his six-year-old son Prince George, saying: "I struggle with Year 2 maths."
The royal couple also spoke to a group of neighbours in mid-Wales who have been offering help with shopping, cooking and deliveries during lockdown.
The prince told the 120 volunteers they had offered "a lifeline" to people in their community.