Visiting Banffshire in the north of Scotland, he paid a visit to Aberlour House, which was once home to the junior section of Gordonstoun School.
Clad in a Rothesay tartan kilt, His Royal Highness sniffed the air. "At least the smell of old socks is gone from here now," he mused.
One would hope so. Since 2004, the building has been the head office of Walkers Shortbread, which manufactures the Prince's own-brand Duchy Originals biscuits.
Aberlour House was a modest stately home, occupied by the Army during the Second World War. In 1947, Gordonstoun's growing prep school moved in, catering for boys from the age of 10 to 13.
Prince Charles did not attend Aberlour House, but joined Gordonstoun later as a boarder.
Gordonstoun and Aberlour House both admitted girls for the first time in 1974, giving rise to the school's most famous alumna.
Its most internationally recognised pupil is not William Boyd, the award-winning novelist; nor Fourth Viscount Rothermere, the newspaper magnate; nor Nick Bateman, the Big Brother evictee.
It is probably not even Prince Charles, despite his international prominence as environmental campaigner and heir to the throne.
No, the title of best-known former pupil must go to Lara Croft - the fictional computer-game heroine - who, as the story goes, was educated at Gordonstoun.