The man of the moment seemed delighted with the white cake – which was decorated with his insignia – at a party thrown in his honour at the British High Commission in Colombo.
CLICK ON PHOTOS FOR GALLERY
Yet despite going through five cakes already, the Prince struggled with cutting the first slice, dropping it upside down.
Camilla revealed in a candid interview that her husband loves birthdays, especially "cake and a bit of a sing song".
But he is difficult to buy presents for, "so he likes to make a list of things that he wants so you get it exactly right."
The couple are in Sri Lanka for a meeting of Commonwealth leaders, following a nine-day tour of India.
It's the second year in a row Charles has been away during his birthday – last year the couple were on an official visit to New Zealand, where Tolkein fan Charles toured the Hobbit set on the day of his 64th birthday.