The sidewalks of London are chaos to a left-brained person.
No one knows which side of the sidewalk to walk. Half try to walk down the left and half walk down the right. It's not a divided highway. It's two streams of fish in constant head-on collisions.
If you walk in the Tube it's evident that native Londoners instinctively walk on the left. It's the same as driving on the left side of the road. Most of the world drives and walks on the right side, but it's ingrained in the UK. It's habitual for Londoners to walk on the left.
The Tube is one thing, the streets are another. The streets are full of tourists and travelers. London is an international city. You have not just visitors from Continental Europe but from all over the world.
This is especially true in the central parts of London around the major shopping and tourist attractions where half the people instinctively, habitually, default to the right. And the other half default to the left.
It would be one thing if everyone was engaged in the flow of traffic. But people are not engaged. They are staring at phones or walking and talking. And others move quickly, on a schedule, squeezed for time.
So imagine two people staring at their phones while walking. One person instinctively defaults to the left to move out of the way, and the other person defaults to the right. It's a collision. There is inefficiency.
There must be an urban street-skill that develops for native Londoners to glide along and instinctively move either left or right. The same way a person develops the skill of avoiding eye contact in a city. In New York you always default to the right. Everyone defaults to the right. In London it takes a certain agility to move either direction.
The best move is to stay to the extreme left or extreme right.
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Paradoxically, on escalators in the Tube, you stand on the right to let faster moving traffic around. Shouldn't you stand on the left? That would mimic the flow of traffic on UK highways where the slowest traffic stays far left, and faster traffic stays far right.
So if you are a slow walker in the Tube, you would walk far left in the halls, but then once you reached an escalator you would stand to the right. Then at the end of the escalator, move back to the left.