In my opinion, probably the most stylish man who ever lived. He definitely wouldn't look out of place today given his love of mixing bold patterns and colours. Yet, for all his eccentricity, he always looked dashing and elegant!
According to Suzy Menkes' book The Windsor Style, while the Duke always prized a dressy, elegant style, he was unlike the Duchess in that he always wanted his clothes to be comfortable. Katell le Bourhis is quoted: "The Duke picked up things from English country life and turned them into fashion for the city. And from the point of view of fashion history, he was the first man to dress in unstructured clothes with no stiffness or interlining." (125-126)