Absolutely delighted I beat a 1800 using the London.
I played a 0 blunder game finally!
Your win has nothing to do with london system
You won because of passed pawns and extra rook
You did not crush the London system, you took advantage of a mistake 16 Qg6 that put his queen as well as his knights in jeopardy. Well played after that.
Besides 12...c4 is not logical: when you have the bishop's pair you do not want to close the position.