Trip Doctor: London's Best Walking Tours
Fox & Squirrel: Itineraries focus on arts and culture and highlight topics such as fashion and food. From $48.
Guild of Registered Tourist Guides: Tours are led by guides who specialize in everything from the monarchy to the music scene. From $213.
London Walks: With more than a dozen drop-in walks daily, it’s perfect for last-minute planners. From $14.