"London Broil" is the name given the first cut of the top round roast. Since is is nearest the sirloin, it is more tender than the rest of the top round. However, as you apparently know, "tender" is a relative term when it comes to London Broil. I would recommend a sirloin tip as more tender and chuck roast as more flavorful -- both are more economical cuts.
Directions: Presuming that you want to broil it ... (Suggest that you click into "According to Smoky" and read the "Glossary" just to make sure) ... then try this marinade: 1 C. Papaya juice or "nectar" Juice of two lemons 2 cloves of garlic, mashed 3 T. Lea and Perrins Worcestershire
1 Cup Papaya juice or "nectar"
Juice of two lemons
2 cloves of garlic, mashed
3 Tbls Lea and Perrins Worcestershire
Generously pierce meat with a fork, then put the meat and the mixture in a plastic lock bag. Refrigerate for 2 to 12 hours or leave at room temperature for not more than two hours. Remove from marinade and wipe throughly dry. If it was refrigerated, let it come to room temperature.
Heat the gill to th max - at least 700 degrees. Place the meat* carefully on the grill and treat it like a steak, (Read "Pursuit of the Perfect Steak" in "According to Smoky.) Remove when the center reaches 135 degrees and let sit for 8-10 minutes before slicing thinly ACROSS the grain.
* Optionally you may rub lightly with olive oil or melted butter before putting on the grill.