The Renaissance-era Villers-Cotterêts castle, in France's Picardy region, is now home to the first cultural site in the world dedicated to the French language, a project championed by President Emmanuel Macron. It's a story conveyed with words, art and architecture to pay tribute to a language spoken by some 320 million people across the globe. But is the influence of the French language still growing? We speak to Xavier North, Hassane Kassi Kouyaté and Barbara Cassin, co-curators of the museum.