Can I think of the Slav as a 'reverse' London, and the Semi-Slav as a 'reverse' Colle-Kowltanalski?

No, other way around!

The Colle-Koltanowski is a reversed Meran with an extra tempo for White and the London is a reversed Slav with an extra tempo.

This is why the Colle and London are inferior to moves like 2.c4.  With 2.c4, White uses his one move advantage to gain space in the center and fight for control of squares like d5.

The London and Colle see White sitting back and playing a Defense with an extra move that often proves pointless and all it does is at best equalizes rather than lead to the typical advantage White gets foe going first.

Actually, I faced a London last night.  I do not have the whole game because it got to a time scramble which I won, but you will see that Black called all the shots this game.

This is very interesting and helpful. Thank you Thrillerfan. And thanks for posting your game! I totally hear what you say about 2.c4 being best. But as a beginner I think Colle and London feel safer. At least for now. And I like the middlegame ideas.

Sorry, cheeky bonus question. So, if the Colle has similarities with Semi Slav meran, and the London has similarities with Slav, what is the pairing for the Torre Attack (which I'm also dabbling in). Thanks, Daniel

having similarity but the plan is totally different.

The Torre has no real counterpart other than possibly the ...Bg4 lines of the Salv as opposed to ...Bf5.

Also, they are really just "reverse" lines when Black plays ...c5, like ...d5, ...e6, ...Nf6, ...c5, and ...Nc6.

The game I posted shows that against other structures, like the King's Indian, it's a totally different game, and not a particularly good one for White.

Against the King's Indian, Torre and Tromp are more annoying than London or Colle, which are nothings against the King's Indian.

This is why I say in many posts that there is no one size fits all in any opening.

London fails against most fianchetto defenses.  Colle fails when the Bishop is outside the pawn chain.

Your best bet, if going non-c4 lines, is as follows:

Against 1...Nf6, you can play the Trompowsky OR

Play 2.Nf3 and against 2...g6 play the Torre, 2...e6 play the Torre, London, or Colle, and against 2...d5, play the Colle, but now if 3...Bf5 or 3...Bg4, you must play 4.c4 and be willing to play a Slow Slav.  There is a problem with the 2.Nf3 move order in the London against 1...Nf6 and 2...d5 but do not recall it, where White is better off delaying Nf3 and getting e3 in early - it has something to do with ...c5 and ...Qb6 lines and the b2-Square.  The Torre is no good against 2...d5 because of 3...Ne4!

Against 1...d5, you can go Colle (but again, must be willing to play Slav against Anti-Colle) or London with 2.Bf4.

Against 1...g6, White has to play 2.c4 or 2.e4 to get anything.

Against the Dutch, 2.Bg5 or 2.g3 are probably best.

Thrillerfan, this is super duper helpful. Thank you very much indeed. And I just watched John Bartholomew analyse a game where he beat the KI using Torre. Torre has real potential against KI. But I'm also looking at learning the Barry against KI as recommended by Summerscale and Lane in their books. Really appreciate your thoughts. Thank you.

dybken, thank you. I appreciate the plans are different. I'd love you to expand please and write more about the contrasting plans between Colle K and Meran, and London and Slav. Thanks.

Your thoughts on the King's Indian Attack?

Sorry, I don't know much about these openings.

But if you play a reverse London against QG, stockfish will tell you it's +1.5.

Also, you almost never play dxc4 in the London system, and one major idea of slav should be dxc4 and your plan is often to expand on the queenside. Again since I don't play either of these two openings so you better watch some introductive video on youtube.

Thank you dybken.

The King's Indian Attack cannot be used as a catch-all system.  For the King's Indian Attack to be effective, Black's LSB must be behind the pawn chain.

There are only 2 defensive against which the KIA is an effective option:

1) French Defense - 1.e4 e6 2.d3 d5 3.Nd2 Nf6 4.Ngf3 c5 5.g3 Nc6 6.Bg2 Be7 7.O-O O-O 8.Re1 b5 9.e5 Nd7 10.Nf1 a5 11.h4 b4 12.N1h2 Ba6 and then White has a choice here.

2) 2...e6-Sicilian Lines - 1.e4 c5 2.Nf3 e6 3.d3 etc.

The KIA is ineffective against virtually any other defense, and especially those where Black gets his LSB outside the pawn chain!

yes, i'll allow it THIS time.

Actual black London (with your white bishop outside the pawn chain,) is a very valid defence in certain situations where white allows you the time. White London is really (as stated above,) a London defence reversed. Slav and Caro Kann do give you similar defensive shapes, and are natural where there's no time to get the bishop out. Pretty different game plans though. As white, London is a thing of beauty for lower rated players, it really helps in developing the habit of over-protection. A lot of aggressive beginners will smash themselves on those rocks. 

Colle, Koltanowsky, London, Torre, King's Indian Attack are not inferior to Queen's Gambit or Catalan. Carlsen, Kramnik and others have played all of these in grandmaster games.
The idea is indeed to play a reverse Slav defence or King's Indian Defence and try to make good use of the extra tempo. So it is indeed the other way around: first there were the defences for black and then some people started playing it in reverse as white.
Here is the stem game of the London opening: a defence as black
https://www.chessgames.com/perl/chessgame?gid=1102115 

Mh

Thanks for all these excellent ideas folks.

This is for MisterWindUpBird.  Very helpful post above. Thank you. But can I just check something  please? When you wrote:

"White London is really (as stated above,) a London defence reversed."

I guess you meant White London .... is  a SLAV defence reversed". Is that right?

And it was also encouraging to read what tyxgc wrote about London/CZ/CK/Torre being sound openings that Carlsen and other top players play.

You are so wrong with that it is beyond funny.

The idea behind the King's Indian Attack is NOT to play a King's Indian Defense and make use of the extra tempo.  The two openings are apples and oranges.

In the King's Indian Defense, the idea is to lure White into blocking the center (d5) and then, with e5 as a safe strongpoint not having to be defended and no risk of the a2-g8 diagonal opening up either, Black goes for a pawn storm with f7-f5-f4, g6-g5-g4, and sometimes h7-h5.  The Bishop is often sacrificed on h3.  And only after breaking open the king position do the black pieces come storming in.

In the KIA, the center is rarely ever blocked.  The "reverse" position would see black pawns on e5, d4, c5 and white pawns on d3 and e4.  This is not what you get at all!

Black has his pawns on c5, d5, and e6.  Not e5.  Therefore, d5 is not weak (unlike d4 in the KID).  There is no use attacking it to try to entice d4.  White will typically play e5 himself.  The center does not wind up completely blocked, and White DOES NOT play f4, and uses the f-pawn to shield his King.  Instead, h4 is played, to open up h2 for the d2-knight and to be able to play Bf4 without fear of ...g5.  White brings his pieces to the kingside to attack the Black King.  White does not storm pawns.  They may eventually advance later on, but it is not an all out pawn storm like the KID is.

Two TOTALLY different Openings!

He has zero understanding of context.

Just because Carlsen plays an opening once or twice does not make it great!  When GMs play a match, for example, they need something with an element of surprise at their level, even if it is not best.

Just because Carlsen played a Colle System (and LOST, by the way) in the 8th round of the world championship match in 2016 does not mean the Colle is just as strong as 2.c4.  Notice he played it ONCE!  He played the Tromposky ONCE (Round 1, which he literally only played because Trump (TRUMPowsky) won a few days prior - he said it himself.

You do not see these players playing any of these openings on a regular basis.  You are better off looking at what GMs play regularly instead of cherry-picking one-off games they played and use that as a basis to play that opening all the time like it is gospel.

I have my own sidelines.  I am an e4-player.  I play the Italian, Closed Sicilian, Nc3 or e5 or 2.d3 against the French, and the Caro is still a work in progress.

Every once in a While, I will throw out a Trompowsky or Sokolsky or some other offbeat opening.  Just because Carlsen played the Trompowsky once in Round 1 of the 2016 world championship does not warrant me to play the Trompowsky in every game that I play White and for me to legitimately stand there and say I can expect a successful chess career playing this as my go-to opening every time I get White!

It is totally laughable when people preach that some offbeat line is legit to play every game you have that color for life on the basis of a cherry-picked game or two!