Peter Sellers stars as Rudolf IV/Rudolf V/Sidney Frewin in this 1979 comedy adventure film loosely based on Anthony Hope's novel. Following King Rudolph of Ruritania's death, General Sapt and his nephew Fritz switch the new king with London cab driver Sidney Frewin to protect him from enemies. As Frewin impersonates the missing King, Princess Flavia becomes his trusted ally and love interest, while Count Montparnasse's wife has a crush on Rudolf.