A ninth role?

In one of the early flashback scenes, we see Dennis Price playing his second role in the film, as Louis Mazzini's (future) father, singing an aria. Louis's (future) mother is also in the flashback, watching from the sofa and making eyes at her future husband.

Next to her on the sofa is Alec Guinness, playing one of the D'Ascoynes, but it cannot be one of the eight for which he is billed. This character is old, at a time before Louis was even born, and must therefore surely be dead by the time that Louis is a full-grown man, not least because by then a younger character, Ethelred (also played by Guinness), is the eighth Duke, which he could not be if his father were still alive. Could this character be the 7th Duke of Chalfont? In any case, however briefly, it seems that Guinness appears onscreen in a ninth role in this film.