Currently playing a game for the "Buying your deels..." achievement. At war with France and I took Paris and Marseille, later losing the latter to loyalty. After capturing Paris, France's capital shifts to Amboise. If I capture Amboise, La Rochelle becomes France's new capital. However when I let Lisbon do my dirty work, France is left with a single city which oddly is not the new capital. In fact, I can propose peace in exchange for her only remaining city.