Monsieur Desjardeaux

In the short story The Terrible Catastrophe, (later chapter 15 of The Big Four), Monsieur Desjardeaux was the Prime Minister of France. Poirot met him and the British Home Secretary Sydney Crowther in order to lay out before them all that he knew about the Big Four. Desjardeaux was, however, highly sceptical about Poirot's claims, particularly as regards Madame Olivier, the famous French scientist, being Number 3. To Desjardeaux, Madame Olivier was a French national heroine and utterly devoted to her work. She could not possibly be involved in an international conspiracy to dominate the world.