Her Grace Commands (1931)

An emancipated Princess, who has just returned home to her court in the Balkans from England, goes in disguise to a servants’ bal and falls in love with an alleged caterer, who turns out next day to be a lieutenant of the guard. Without letting on to her masquerade, she makes sure he climbs the ranks quickly. At the same time, she tries to thwart her engagement to an unpopular prince.