The Duke and Duchess of Cambridge put their artistic skills on display as they visited a mental health event in London.
William joked that he and Kate might have "ruined" a picture being painted during the two-day Global Ministerial Mental Health Summit.
The royal couple both somewhat nervously added a single brushstroke to Dairo Vargas artwork after meeting people working to raise awareness of mental health issues around the world.
Following Kate’s handiwork, William told his wife, much to her amusement: "That's pretty much ruined the picture."
After picking up the paintbrush himself he then told the artist: "This is how you properly ruin a picture."
When Mr Vargas invited the pair to add to the painting, Kate told him: "This is very brave of you."
Political figures, experts from around the world and policy makers are attending the event to discuss issues such as how to deal with the stigma attached to mental health.
Another policy up for discussion at the summit, which is co-hosted by the UK Government and the OECD, is a declaration committing to putting mental health on an equal footing with physical health.
William and Kate have long been involved in mental health initiatives through their Heads Together campaign.
They were reunited on Tuesday with Elisha London, who worked on that campaign, as they learned about a Zimbabwean project called the Friendship Bench.
The trio sat on a replica bench to the original one in the project which started in Harare, as Ms London explained how so-called “community grandmothers” – people trained to help those experiencing mental health problems – listen to and support locals within their communities.
Alexandra Almeida, from the My Mind Our Humanity campaign as part of the Lancet commission on global mental health, said it was "very nice" to meet William and Kate and have their support.
Ms Almeida, from Portugal, said: "They wanted to know if we feel there has been a change in mental health and how the young people view mental health in Britain and other places across the world."
Ahead of the summit, the Department of Health and Social Care began a social media campaign using the hashtag #TheWorldNeeds to ask people what needs to change in the way mental health is treated and perceived.