Originally, this term referred to a beef flank steak that is marinated and then broiled or grilled. The flank steak traditionally used for the London Broil is a large cut of meat that can be rather tough, which is the reason for marinating the meat before cooking. When served, the London Broil is cut into thin slices across the grain at a 45° angle. London Broil is now commonly used to refer to several other boneless cuts: a beef top round steak and the chuck shoulder steak. The top round, which comes from the upper leg, is lightly marbled, while the chuck shoulder is marbled with more fat and generally more flavor.