Realistically, there were eight. Four of them were francophones: Sir Wilfrid Laurier, Louis St. Laurent, Pierre Trudeau and Jean Chretien. Four were English: Joe Clark, Brian Mulroney, Paul Martin and Stephen Harper.
The PM with the broadest facility for languages was English-speaking Sir Robert Borden who had a working knowledge of French, German, Greek and Latin.
certainly neither mackenzie king nor diefenbaker. how about poyglots . trudeau could get by in spanish too.
No doubt, several Prime Ministers — like Trudeau — had some working knowledge of additional languages. It’s always difficult to decide the point at which it’s a working language for them. Thanks for responding.