Luck does not come into chess...
I'm sure it definitely does.
I don't know, what is luck in this case? If I blunder my queen against a 1200, it seems like I can connect my loss to whatever made me blunder the queen in my head. In other words I can blame me for it. I may not normally make the mistake, but it doesn't change who to blame for it. This, of course, does not suggest that the 1200 is a better player, but it does mean that, on this rare occasion, the 1200 played better than me.
If you mean luck in the sense that something like this happens when in most cases it wouldn't happen, ok. When humans apply skill blunders can still happen -- that's just a cute trait of ours that the machine doesn't share; these situations are luck in the sense that they are hard to predict, but the fact that it's the same me playing the game, just as much as in a game where I don't blunder, is obviously intact.
I guess in other words... I don't see why, just because someone may beat another person 2% of the time, means there is something special about that 2% (like luck). It's rare, sure, but I don't see why that alone is so important. If it's rare, it means it's rare, does it really mean anything else? In 98% of the games he gets fairly beaten, while he wins fairly in the other 2%, just that one happens less frequently than the other. I mean sure if you bet on the guy who wins 98% of the time and he loses, you had bad luck in terms of the statistics misleading you, but I feel like that changes the subject. The 98% chance could be argued to be a natural consequence of the amount of skill the player had.
Despite having very little respect, I've gotten quite a few good games out of the London System.