Tenderize the steak by piercing the meat with a needle tenderizer, a fork or a paring knife all over both sides of the top round beef. Generously season both sides of the meat with salt and freshly ground black pepper and place the steak into a zipper sealable plastic bag or non-reactive container.

Make the marinade by whisking together the olive oil, red wine, Worcestershire sauce, soy sauce, Dijon mustard, brown sugar, garlic, thyme and parsley. Reserve and set aside ⅔ cup of the marinade to use as a basting sauce for grilling. Pour the rest of the marinade into the bag or container with the steak. Seal the bag or cover with plastic wrap and refrigerate for at least 8 hours or overnight. Flip the meat over a few times during the marinating process.

Remove the meat from the refrigerator 1 hour before grilling.

Place the reserved, unused marinade in a saucepan and simmer for a few minutes to reduce and thicken the sauce.

Pre-heat the grill or stovetop grill pan to medium high heat. Remove the steak from the marinade and discard the marinade.

Grill the steak for about 15 to 20 minutes for rare and 20 to 25 minutes for medium, adjusting to accommodate the thickness of your particular steak. Flip the meat over once or twice and baste with the reduced sauce. The meat should register 130°f to 140°F with an instant read thermometer. (If using a stovetop grill pan, sear the London broil on each side for a 2 to 3 minutes then transfer to a 400°F oven for 15 to 20 minutes to finish cooking.)

Remove the London broil from the grill and loosely tent with foil. Let it rest for 10 minutes before serving. Then, carve it into thin slices across the natural grain of the meat. Transfer to a serving platter, pour or brush any remaining basting sauce over top and garnish with some fresh sprigs of thyme and chopped parsley.