If your grocer has labeled the cut of meat you have as London broil, skip to the next paragraph. To purists, London broil is a preparation, not a cut of meat. It is a steak that is pan-fried (and therefore not grilled) over high heat only to medium rare, beyond which point it becomes inedibly tough. It is a useful preparation for lean, tough cuts of meat, such as flank steak, shoulder, and round. To the less pure, London broil is a preparation that involves marinating a flank steak, then grilling, broiling, or pan-frying it. Some absolutely promiscuous butchers label various cuts of meat London broil, including flank steak, sirloin tip, top round, etc. We’ll assume you have a flank steak. For best results, marinate the meat for several hours or overnight in the refrigerator in the marinade of your choosing. It is easiest to put the marinade and meat in a sealable plastic bag. Turn the bag over once or twice. When you are ready, grill the steak over high heat for about 3 minutes per side, then turn the grill down to medium if using gas or move the steak to a cooler area if using charcoal, and cook for another five to six minutes, turning it once midway. Finally, for a flank steak, the grilling is less of an issue than the cutting. Flank steaks are tough, so you slice them thinly on a diagonal across the grain to sever the tough fibers and make the flavorful steak chewable. grilled marinated london broil For marinade 4 large garlic cloves, minced 4 tablespoons balsamic vinegar 4 tablespoons fresh lemon juice 3 tablespoons Dijon mustard 1 1/2 tablespoons Worcestershire sauce 1 tablespoon soy sauce 1 teaspoon dried oregano, crumbled 1 teaspoon dried basil, crumbled 1 teaspoon dried thyme, crumbled 1/2 teaspoon dried hot red pepper flakes 2/3 cup olive oil a 2- to 2 1/2 pound London broil Preparation Make marinade: In a bowl whisk together marinade ingredients until combined well. Put London broil in a large resealable plastic bag and pour marinade over it. Seal bag, pressing out excess air, and set in a shallow dish. Marinate meat, chilled, turning bag once or twice, overnight. Grill meat, marinade discarded, on an oiled rack set about 4 inches over glowing coals, turning each once, 9 to 10 minutes on each side, or until it registers 135°F. to 140°F., on a meat thermometer for medium-rare meat. (Alternatively, meat may be broiled.) Transfer meat to a cutting board and let stand 10 minutes. Cut meat diagonally across the grain into thin slices.