The Duke of Cambridge has revealed he has been secretly working as a volunteer supporting people contacting a crisis helpline developed by his Royal Foundation.

William’s work with Shout 85258 – a round-the-clock text messaging helpline – was announced to mark Volunteers Week.

Last month, the duke and duchess marked the service’s first anniversary by speaking to some of its volunteers via video call, and William said: “I’m going to share a little secret with you guys, but I’m actually on the platform volunteering.”

Kate has also been helping others and has taken part in “check in and chat” calls with those self-isolating or vulnerable as part of the Royal Voluntary Service’s NHS Volunteer Responders scheme.

A royal source said the Cambridges would be carrying out official events via video calls for the foreseeable future but they were hoping to resume visits in person at some point.

“As with other royal households we are looking at ways we can do physical engagements in the future in line with Government guidance,” the source said.

The biggest issue was trying to organise royal engagements in a way that did not attracts crowds or put pressure on police resources, the source added.

The duke is one of more than 2,000 crisis volunteers who are trained to support anyone, whatever their crisis, chatting via text message and helping people sort through their feelings by asking questions, empathising and listening.

The Cambridges and the Duke and Duchess of Sussex helped to launch the crisis line in May last year, investing £3 million in the service through their Royal Foundation.

More than 300,000 text conversations have taken place between volunteers and people needing mental health support, with around 65% of those texting aged under 25.

It is understood that Kensington Palace had previously been reluctant to say whether William was volunteering for the service because it feared Shout might be overloaded by people hoping to discuss their troubles with the future king.

But Shout is now geared up to handle an expected increase in demand for the service.

The couple marked Volunteers Week by chatting with the Machynlleth Community Corona Response Group, and in a lighter moment the duke joked about coronavirus panic buying, asking: “Can any of you explain to me why all of us were bulk buying toilet roll?”

More than 120 volunteers in the mid-Wales market town of Machynlleth and surrounding villages go shopping for neighbours, man a telephone helpline, and cook and deliver nourishing meals for the vulnerable.

In the video call made on Wednesday, William praised their efforts after the couple had spoken to 91-year-old great-grandmother Lynda Edwards-Ryley, who was lonely and isolated before volunteer Sadie Maud offered her support.

The duke said: “It’s National Volunteering Week and we want to say a big thank you from both of us. Thank you for all the volunteering you’re doing, thank you for all the time and all the effort you’re putting in.

“It’s been hugely rewarding and important that you guys are doing that and, as we’ve heard from Lynda, all of you have been a lifeline to all the people who you’ve helped in the area.”

The Cambridges also spoke to Conscious Youth, an organisation working with young people from mainly black and other ethnic minority backgrounds in West Yorkshire, and joked about the challenges of home schooling.

The couple have not disclosed if they have sent their children back to school, but William admitted some of Prince George’s coursework has proved daunting at times.

“I struggle with Year 2 maths,” he said.

Sophie Simpson, 38, who co-founded Conscious Youth with Serena Johnson, 35, said: “The duke and duchess totally agreed that teaching Year 2 maths was very difficult. I could agree with them because I teach that as well and I’m struggling.”

Their organisation, created in 2016, has set up a virtual youth club on a website during the coronavirus pandemic to support young people through the crisis.