After arriving at Stewards Academy in Harlow, Essex, Vice Lord Lieutenant of Essex Jonathan Douglas-Hughes, accidentally tripped and fell over.
The retired 72-year-old lieutenant was dressed in full uniform when he stumbled backwards over a bollard.
William immediately rushed to his aid and helped him get back on his feet.
“I’m fine, thank you,” the dignitary said later. “The Duke was very concerned, but I reassured him I was perfectly all right.”
The couple was there to support the Heads Together campaign, which deals with raising awareness around mental health problems.
During the visit, Kate, who wore a knee-length blue patterned dress by designer Altuzarra, charmed once more with her radiant smile.
Inside the facility, the pair attended a course with students and mentors and the Duke gave a short speech.
The royal took the opportunity to show his humorous side by revealing that he still acts like a teenager.
“Sometimes I still feel like I am 16, to be honest sometimes I still act like I am 16,” the prince said while chatting with parents, and Kate agreed: “I still think you’re 16.” [via HELLO!]
“Yes, Catherine often tells me that,” he joked.
The royals were impressed with the system set up by the Stewards Academy, in which each new student of the institution is assigned to an older one in order to facilitate integration.