The Duke of Wellington was assured of victory in battle 
whenever he wore his special headgear.

I enjoy the understatement in this BBC news magazine explanation of this phenomena:

"The placing of traffic cones on historic statues can be blamed on two factors – alcohol and the prevalence of roadworks of some kind in city centres."

It’s a funny and relatively harmless prank – unless the prankster falls off while attempting to hat the statue.


 Queen Victoria wishes to thank her milliner.

Dignity.
Pure dignity.

Actually, pranksters may not be responsible. It could be this guy:


"I say traffic cone on statue head is 
religious ritual! What say you?"

(And in a side-note, the artist prankster responsible for creating the above monster in North Carolina was charged with "misdemeanor larceny" for repurposing the barrels from a construction site. I wish him a long and successful monster-creating career.)

– Why do people put traffic cones on statues?, BBC Magazine Monitor>> – Barrel Monster Bust. Cops: Man created public art with items swiped from construction site, The Smoking Gun>>