However (you knew that was coming, didn't you), because of a personal dilemma, I've had to rethink this pruning and topping subject. Of couse, my newfound knowledge of pollarding may enable me to once again be a snob.
I have a sycamore tree that my generous older brother gave me to plant for quick shade when we moved to a house which had no shade trees. My intent was to plant the sycamore for quick shade near the house, then cut it down when another, slower-growing tree a little farther from the house had time to get some size. The sycamore turned out to be a good climbing tree, so I promised my son I would not cut it down before he turned 18.
My generous older brother also happens to be quite knowledgeable about trees, and he let me know that cutting back sycamores is common in Europe where they call the sycamores plane trees and call the process pollarding. I adapted the process to my situation and sent my dear son up the tree with a bow saw.
He cut the top out. The tree sure looked funny with a V-shaped gap in the top the next summer. But the following winter, Caleb trimmed back some of the upper limbs to give it a little better shape. This is what it looked like this past winter. (You can also see pine limbs in the yard from three pines that were cut by professionals. The tree with the cinnamon colored bark is an unmolested crepe myrtle.) Click on the image to enlarge.
This is how the sycamore looks today.
If you want to see the professionals pollard a London plane tree, check out this time lapse video. It is amazing to me.
If this topic has piqued your interest, you ought to do a web search of pollarded tree images. You can see all kinds of trees with grotesque knobs that would give the "crepe murder" opponents heart attacks.