For people who do not know what the London System is: It is a basic opening using white's Queen Pawn and then Bf4 (or after a few moves) which forces the game to the middle game. Due to not resulting in a closed game, it is also criticized and called the old man's system or boring system
As described by a Grandmaster and author of the main used book about the London System (Vlatko Kovačević):
"Basically the London is a set of solid lines where after 1.d4 White quickly develops his dark-squared bishop to f4 and normally bolsters his centre with [pawns on] c3 and e3 rather than expanding. Although it has the potential for a quick kingside attack, the white forces are generally flexible enough to engage in a battle anywhere on the board. Historically it developed into a system mainly from three variations:
1.d4 d5 2.Nf3 Nf6 3.Bf4
1.d4 Nf6 2.Nf3 e6 3.Bf4
1.d4 Nf6 2.Nf3 g6 3.Bf4."