Kate Middleton and Prince William Couldn't Stop Giggling at the Global Mental Health Summit

On Tuesday in London, Prince William and Kate Middleton attended the Global Mental Health Summit. Mental health initiatives are close to both of the royals' hearts, and today marks their first joint engagement together since Kate gave birth to Prince Louis in April.

Kate recycled a gorgeous lilac Emilia Wickstead dress (you can shop it here)—the same one she was spotted in last year while holding hands with Princess Charlotte (and caring for her when she fell) as she, Prince George, and William boarded a helicopter.

Both Kate and Wills are clearly very excited to be back at work together. The royal couple couldn't stop laughing and smiling throughout the day, though they kept the physical PDA to a minimum. Royal reporter Rebecca English captured the adorable moment the Duke and Duchess were told to "act natural" for the cameras, and they just couldn't hold it together.

Here's the video:

Then the moment was documented in a perfect series of photos:

Will also immediately told artist Dario Vargas that Kate is "the arty one," which lightened up the mood. The Duke and Duchess of Cambridge clearly look very relaxed and at ease.

During the summit, the Duke and Duchess went to a workshop about a U.S. initiative that would provide mental health outreach for mothers. This feels incredibly fitting for Kate, who just returned from six months of maternity leave.