article_snippet: But critics of cannon warn that in incidents on the continent they have led to serious injury and even death.
article_snippet: In one case in Germany a man was blinded and in another a protester was stunned and then killed after being run over.
article_snippet: Calls for their introduction came during the 2011 riots and later student protests in the capital.
article_snippet: Mr Johnson has previously urged police to get 'medieval' on rioters, and said officers must never again be left powerless in the face of overwhelming violence like that seen during the 2011 riots.
article_snippet: Police said it could have helped protect firefighters and paramedics after shops were set ablaze as rioting spread to Croydon in 2011.