Kate Middleton and Prince William Step out for Their First Royal Event Together Since Prince Louis' Birth

Prince William and Kate Middleton stepped out on Tuesday, Oct. 9 for their first joint royal engagement since the birth of their son Prince Louis in April, with the Duke and Duchess of Cambridge attending the inaugural Global Ministerial Mental Health Summit.

The summit saw political figures, academics and policymakers discuss issues surrounding mental health, with the event working to help countries work together to address said issues.

William and Middleton have been vocal about their advocacy for mental health, starting their Heads Together campaign, along with Prince Harry, and aiming to combat the stigma surrounding mental health.

The royal couple arrived to attend multiple presentations on case studies of active mental health programs and also met with young people to speak about their experiences with mental health.

They also visited a "friendship bench," which was a Zimbabwean project that aimed to teach older women in the country how to help those struggling with mental health with talks on the benches. The initiative was started by Dixon Chibanda and teaches the women to become lay health workers.

During the event, William aimed a good-natured ribbing at his wife after Middleton, who studied art history at the University of St. Andrews in Scotland, added a brushstroke to artist Dairo Vargas' painting.

"That's pretty much ruined the picture," William joked, via E! News, before poking fun at his own attempt and adding, "This is how you properly ruin a picture."

For her appearance, Middleton wore a lavender Emilia Wickstead dress and carried a crocodile Aspinal of London handbag, accessorizing her ensemble with nude pumps, silver earrings and a matching necklace. The Duchess previously wore the dress, named the "Kate," during an appearance in Hamburg, Germany last summer when she and William took a royal tour with children Prince George and Princess Charlotte.

Middleton attended her first solo royal engagement since her son's birth last week, when she visited the Paddington Recreation Ground in Ewhurst, England to spend time with local school children.

Also this week, the Duchess is expected to appear at the Victoria & Albert Museum on Wednesday for her first visit as a royal patron of the institution, and she and William, along with George and Charlotte, are slated to attend Princess Eugenie's wedding to Jack Brooksbank on Friday at St. George's Chapel at Windsor Castle.

Photo Credit: Getty / Karwai Tang