"I love the photo of the undercover ducks!!!" one royal fan wrote, while another added: "The person responsible for Clarence House social media today should definitely get a promotion!"
The 70-year-old also gave a speech during his visit.
"To you, walking in past the razor wire each day becomes routine," he said. "But I hope that you will never lose sight of the fact that you are part of an extraordinary, world-leading organisation that has achieved remarkable things during its proud one-hundred-year history, and which will continue to play an indispensable role over the century to come."
It's been a busy month for Charles and Camilla.
The royal duo recently returned from a trip to Wales and attended grandson Archie Harrison’s christening on Sunday.
WATCH: MEGHAN'S SECURITY TELL FANS TO STOP TAKING PHOTOS OF DUCHESS!