The London System can be thought of in some ways as a Slav Defence with reversed colours. Since the Slav is considered a perfectly sound defence for Black, there is nothing inherently wrong with White adopting a similarly solid structure with an extra move.
In theory, White has the first move and might therefore be expected to play more ambitiously for space and an early advantage. In practice, however, the London System has some very useful qualities of its own.
One advantage is that it can take an opponent away from the positions they have prepared most thoroughly. A player facing 1.d4 may be expecting to play a King’s Indian Defence, Nimzo-Indian Defence, Benoni or one of the many variations of the Queen’s Gambit. Against the London System, White often develops in a solid and relatively controlled way instead.
This can make it more difficult for Black to produce something immediately sharp or forcing from opening preparation alone.
One of the attractions of the London System is that White can often reach a familiar structure against several different Black setups. Developing the dark-squared bishop early, building a solid centre and completing development can give White a position that is relatively easy to understand.
This does not mean, however, that White should simply play the same moves automatically regardless of what Black does.
That is an important distinction. Learning a typical setup can be useful, but understanding the purpose of the moves is much more valuable than memorising where the pieces normally go.
Black’s choices should influence White’s decisions. If Black challenges the centre quickly, delays castling or chooses an unusual piece arrangement, White needs to react to the actual position rather than simply continuing with a predetermined sequence.
The solidity of White’s centre can sometimes make it easier to organise an attack against a Black King that has castled Kingside.
White may be able to bring pieces towards the King and, in suitable positions, consider advancing Kingside pawns. Because White’s central structure can be quite stable, there may be less immediate danger involved in directing pieces towards an attack.
However, White should not assume that a Kingside attack is automatically justified simply because the London setup has been reached.
This is where Black can be flexible too. If Black delays castling or castles Queenside in an appropriate position, White’s intended Kingside attack may lose much of its purpose. Pawns that White has advanced aggressively could even become weaknesses.
A good London System player therefore still needs to judge the position rather than simply following a standard attacking plan.
From Black’s point of view, I strongly favour challenging White’s centre rather than allowing White to complete an ideal setup without interference.
For this reason, I like an early …c5.
This is a principled move because it immediately questions White’s central structure. In some respects, the resulting ideas can resemble a Queen’s Gambit with colours reversed.
Black may also develop the Queen to b6 in suitable positions, putting pressure on the b2 pawn and forcing White to think carefully about how to defend it. Depending on the pawn structure that develops, Black may later have opportunities for Queenside play or even ideas resembling a minority attack.
The exact plan will depend on White’s move order, but the general principle is important: Black should try to create active counterplay rather than simply watch White assemble the standard London setup.
The London System is sometimes presented as an opening that allows White to avoid learning much theory. There is some truth in the idea that White can reach familiar structures without memorising enormous numbers of variations.
But that does not mean the opening requires no understanding.
Once the opening moves have been played, White still needs to decide where the pieces belong, whether a Kingside attack is appropriate, when to challenge the centre and how to react to Black’s counterplay.
The resulting middlegames can be quite different depending on what Black chooses to do.
This is one reason I think the London System is more interesting than it is sometimes given credit for. The basic structure can be straightforward, but the positions still require judgement.
As with any chess opening, I think it is much better to understand the ideas than simply memorise a sequence of moves.
A player who knows that the bishop normally goes to f4 but does not understand why it belongs there will eventually struggle when the opponent does something unexpected.
A player who understands White’s central structure, typical piece placement, Kingside possibilities and Black’s main counterplay is much better equipped to deal with unfamiliar positions.
The same applies from Black’s point of view. Rather than trying to memorise a single system against the London, I would concentrate on understanding how and when to challenge White’s centre, particularly with …c5, and on avoiding passive play.
Overall, I regard the London System as a perfectly sound opening. It may not always be White’s most ambitious choice, but it can lead to strategically interesting positions and can be particularly effective against opponents who are more comfortable with the main theoretical responses to 1.d4.
The important thing is not to treat it as an opening that plays itself. Knowing the standard setup is only the beginning; understanding the plans for both sides is what makes it useful.