The statue of a dog that caused riots in Trafalgar Square
It all began when Professor William Bayliss took part in an experiment on a brown terrier dog at the University of London in the the early 1900s. Anti-vivisection campaigners who had infiltrated his lecture protested that the dog was not properly anesthetized -- which was totally illegal, even then. A memorial statue of the brown dog was then erected in Battersea in 1906... that was when the rioting started.
Repeatedly attacked by medical students (who objected to its anti-medical inscription), it became necessary to have a nightly police guard for the statue. The rioting reached a peak with an attack on the statue by 100 statue-hating students. Another group of 1,000 students was meanwhile in Trafalgar Square, their protest turning into a battle against a force of 400 police, many on horseback. Tired of the controversy -- and the expense -- Battersea council demolished the statue in 1910 under cover of night, and more than 3,000 people demonstrated in Trafalgar Square to protest that, too. This replacement was erected in Battersea Park in 1985. No one has rioted over it. Yet.