Agent Peacock: He dresses to outshine the girls, appears late at balls because he lost his time trying to tie his cravat just right, and generally dismissed as a fop. Has snagged the hottest redhead in Europe as his wife, and all the ladies fawn over him, his Camp posturing, and his slender white hands that are dainty enough to pass as a woman's. Also happens to be the ultra-badass secret vigilante who pulls off daring rescues of French aristocrats on a regular, if not daily, basis.
Historical Villain Upgrade: The historical Marquis de Chauvelin was the deputy French ambassador to Britain in 1792. Chauvelin the character has almost nothing else in common with him.
It's Personal: His repeated failures to capture the Pimpernel mean that his power and influence steadily decrease through the series. This leads him to become increasingly obsessed with capturing the Pimpernel.