As much as I love to disagree with Chef Carey he is correct. London Broil is a preparation. It is usually done with skirt, flank and at times sirloin. The meat in marinaded, broiled and sliced thinly before presentation "Meat cutters" might call it that but trained butchers would not. Customers might ask a butcher for it but it is not the name of the cut.
Yes, we all know that, but I am stating that in my neck of the woods, a particular cut of meat is, indeed, labeled London Broil. Also, if you Google "London Broil" you will see many references to it as a cut of meat. This site is one of several I found.
http://www.cooks.com/rec/view/0,1626,134179-251192,00.html