MANCHESTER, England (Reuters) - Britain is worried by violence during a banned referendum in Spain s northeastern region of Catalonia but sees the vote as unconstitutional, Foreign Secretary Boris Johnson said on Sunday.  We are obviously worried by any violence but clearly the referendum, as I understand it, is not constitutional so a balance needs to be struck,  Johnson told Reuters.  We hope very much that things will calm down.  
Britain worried by violence in Catalonia but says vote was not constitutional: Johnson