London Broil is usually flank steak, although the term is used for any thin cut of meat that is broiled or grilled and sliced on the diagonal, or bias. Be sure always to slice London broil into thin strips and on an angle to cut through the lengthwise fibers. For six servings, you may have to buy two pieces of meat for three-and-a-half pounds.
Stir together the tomato juice, Worcestershire sauce, horseradish, sherry, marjoram, basil, and pepper in a small bowl.
Place the steak in a single layer in a glass or ceramic dish. Spoon the tomato juice mixture over the meat, spreading to cover. Turn the meat to coat the other side. Cover and refrigerate for at least 2 hours or set aside at room temperature for no longer than 30 minutes. Turn the meat once or twice and return to room temperature if refrigerated before grilling.
Prepare a charcoal or gas grill. Lightly spray the grill rack with vegetable oil cooking spray. The coals should be moderately hot to hot.
Lift the meat from the marinade and discard the marinade. Grill the steak for 8 minutes. Turn the steak and grill for 7 to 10 minutes longer for medium rare, or until it reaches the desired doneness.
Let the steak rest at room temperature for about 5 minutes before slicing on the diagonal into thin strips.