The term: "London Broil" is not a cut of meat, it is a form of cookery - to broil a cut of meat to a medium rare to rare doneness to improve its tenderness. It originally started with flank steak, which, when overcooked, was tough and chewy because of the long, fibrous meat fibers. But, when broiled quickly to brown the surface but leaving the inner fibers rare and undercooked, the overall effect was to improve the tenderness of the cut. Likewise, the method of cookery spread to other lean cuts such as thick-cut top round, bottom round, beef arm shoulder, shoulder clod and eye round split lengthwise, etc.,, the London Broil method of cookery applied as well, to take a less tender cut of meat, broil it rare to medium rare over high heat, slice it across the grain in thin slices and serve with its own juice.