Allowing the meat to rest before carving; it makes the meat more juicy. The reason you let the London broil marinate at room temperature on the counter versus at forty degrees in the refrigerator is quite simply that when you expose cold meat to heat, the outside cooks dramatically faster than the inside of the meat What happens is the outside meat becomes over cooked while the inside is still not done. By the time this is finished it will be a tough piece of meat. Raising the internal starting temperature even 30 degrees to the temperature of the counter allows for the out side of the meat to cook at the same rate, but allows the internal temperature to raise equally, leading to a more tender piece of meat in the end. On a London broil, which is already tough to start with, we want to do everything we can to reduce toughness. Also, we want to let the London broil rest at room temperature because there are little enzymes in the meat that will break down the tougher parts resulting in a more tender meal. They only work at warmer temperatures under 120°F. This has been proven through food science and the preparation technique known as Sous Vide. Pronounced Sue Veed. In this recipe, it might be prudent to finish the chemo-patient's London Broil in a saute pan after cooking allowing it to raise to a well done temperature of 150 degrees to prevent food borne illness.