Larry Your London Broil looks marvalous & I would love to dive in for seconds. I like a darker crust than your pics show & I like a crisp bark too.
Using the reverse sear It would be hard to achive a darker crisp crust & not overshoot a 120deg rare internal. My favorite steak is to duplicate a Ruth Criss steakhouse type of finish on the meat. Grill marks look great but a sear in a hot skillit over charcoals will come closer to what I'm looking for. Larry I'm not tryin to start no argument I'm only pointing this out for others to take into consideration. Every method of grilling will yeild different results.
Here is a PM I sent to Surfinsapo on this subject:
Glowing hot charcoal briquettes hit 800 to 1000 deg, The trick to a perfect steak is sear from the top, this is what a comercial salamander does. This stops the heat from rising from an under the meat heat source which give inconsistant results. The other + is even radiant heat up to 1200deg if needed.
http://www.wisegeek.com/what-is-a-salam ... roiler.htm
Then in restaurants they finish the steak in the oven to the costomers liking. This does 3 things It puts wonderful crust on the outside, the crust is the same depth on both sides & the red or pink center is centered & consistant throughout the cut. When we grill steaks at home its tricky to be consistant every time. What I do is quick sear the meat as close to the coals or fire as possible on both sides, bring the remove from the grill & place on a warm plate with a pat of butter or Maitre D'hotel butter cover & let rest. This will make a rare steak For med put it in a 350deg oven for about 5 min.