During a Nelson celebration I was standing in Trafalgar Square with a friend of puzzling proclivities. 
He had for some time been gazing at the column in an abstracted way, and seemed quite unconscious of the casual remarks that I addressed to him.

"What are you dreaming about?" I said at last.

"Two feet——" he murmured.

"Somebody's Trilbys?" I inquired.

"Five times round"

"Two feet, five times round! 
What on earth are you saying?"

"Wait a minute," he said, beginning to figure something out on the back of an envelope. 
I now detected that he was in the throes of producing a new problem of some sort, for I well knew his methods of working at these things 

"Here you are!" he suddenly exclaimed. 
"That's it! 
A very interesting little puzzle. 
The height of the shaft of the Nelson column being 200 feet and its circumference 16 feet 8 inches, it is wreathed in a spiral garland which passes round it exactly five times. 
What is the length of the garland?
It looks rather difficult, but is really remarkably easy."

He was right. 
The puzzle is quite easy if properly attacked. 
Of course the height and circumference are not correct, but chosen for the purposes of the puzzle. 
The artist has also intentionally drawn the cylindrical shaft of the column of equal circumference throughout. 
If it were tapering, the puzzle would be less easy.

See answer