Like most royals, the Duchess of Cambridge's accessory of choice is a clutch. Kate keeps different styles in rotation, from solid colours to prints, and she usually matches them to her dresses and skirt suits.
According to Myka Meier, founder of Beaumont Etiquette, the duchess carries a clutch so she can "hold her bag in front of her in both hands when shaking hands might be awkward." But she likely has a good fashion reason for only carrying clutches too: they simply look more polished. After all, we can't exactly imagine Kate lugging around a giant tote bag for her royal engagements.