Openings
The London is solid but not scary. Because White plays the same setup against everything, you can prepare clear, reusable plans as Black.
An early ...c5 challenges White's centre directly. Combined with ...Nc6 and ...Qb6, you pressure both d4 and the sensitive b2-pawn at once — a recurring theme against the London.
Because the Bf4 has left the queenside, ...Qb6 attacks b2 and d4 together. White usually must answer with Qc1, Qb3, or b3, all slightly awkward. This is one of the most annoying tries for a London player to face.
Trading off White's good dark-squared bishop takes away the London's main attacking piece. ...Nh5 hitting the Bf4, or meeting it with your own ...Bd6 to offer a trade, both reduce White's kingside pressure.
Setting up ...g6 and ...Bg7 is a calm, sound approach. Your bishop eyes d4 and the long diagonal, and White's standard kingside ideas lose much of their bite.
Don't play passively and let White get the dream Ne5-and-f4 setup unchallenged. Stake a claim in the centre early. Pick one of these plans, try it in a free game, and you'll find the London far less intimidating.
Challenge d4 early with ...c5, and use ...Qb6 to hit both d4 and the b2-pawn. Trading off White's dark-squared bishop with ...Nh5 or ...Bd6 also blunts the London's main attacking idea.
Because White's dark-squared bishop has gone to f4, the b2-pawn is loose. ...Qb6 attacks b2 and d4 at once, forcing White into a slightly awkward defensive move.