Prince William, Duke of Cambridge, revealed he has secretly been volunteering to assist people struggling with mental health issues during the coronavirus lockdown.

The Duke has been volunteering with Shout, the United Kingdom's first 24/7 crisis text line that launched in May 2019. The organization was launched by The Duke and Duchess of Cambridge and The Duke and Duchess of Sussex following a £3 million investment from The Royal Foundation, a statement from Kensington Place read.

"I'm going to share a little secret with you guys, I'm actually on the platform volunteering," Prince William told Shout team members during the video call that took place last month.

Kate has been volunteering herself to help with "check in and chat" calls for those who are self-isolating or vulnerable, Kensington Palace announced.

The calls are part of the Royal Voluntary Service's National Health Service Volunteer Responders program, which was set up to support the National Health Service and those vulnerable to COVID-19, according to the announcement.

Prince William has been very vocal in the past about mental health. In January, he narrated a one-minute video encouraging millions of soccer fans to think about their mental health. Last year, he spoke openly about the loss of his mother, Princess Diana, for a BBC documentary on mental health and how men should feel comfortable discussing the topic.

In 2018, the Duke launched the website Mental Health at Work, which provides resources and tool kits to improve mental health in the workplace.