The 36-year-old Duke of Cambridge stopped by the Royal London Hospital on Wednesday -- where he was announced as the patron of the air ambulance’s anniversary campaign -- and assured some gathered children that he was fully aware of Kate's 37th birthday.
The sweet moment came when some kids gave William a birthday card to give to his wife of more than seven years, which was captured on video by royal reporter Rebecca English. "Thanks for remembering," he quipped.
"I did remember this morning so I was OK," he clarified. "But that's brilliant. Thank you so much."
He continued praising the children, telling them, "Your writing's very good as well."
The proud dad also held up what appeared to be another birthday card for Kate, commenting, "Look at these, they're amazing... These are beautiful. Charlotte's gonna love this. That's amazing. Thank you very much."
Watch the video below for more on the royal family: