[%c_effect h4;square;h4;type;Interesting;persistent;true] In this particular situation of the London this move is rare. But the whole concept is the key to fighting the Grunfeld setup nowadays.
1. d2d4  1... g8f6  2. c1f4  2... d7d5  3. e2e3  3... g7g6  4. g1f3  4... f8g7  5. b1d2  5... e8g8  6. c2c3  6... b7b6 