In London it's generally understood that you stand on the right of an escalator and walk on the left. It allows people in a hurry to move faster and those who want a more relaxed ride to avoid getting in the way of more urgent travellers.
The thing is, you don't really find this in other areas of the UK. So how did this behaviour/understanding become established?
Do you really think this is something unique to London? The same escalator etiquette exists in several major European cities I've visited.
The same practice exists throughout the US. I see it all the time in Chicago. A very similar practice has also existed among drivers on many US roads for a very long time. Slower traffic holds to the right, while the left is reserved for passing. Because of its similarity, I seriously doubt the escalator etiquette you describe originated in London.
The same etiquette exists in the US and in Japan. There are signs that tell you which side to stand or walk on.
In Australia it isn't locked in, but the etiquette is to stand on the left and overtake on the right. I should point out that this reflects motor vehicle traffic where you overtake on the right, and on multi-lane roads are required to keep left unless passing slower traffic.