Spanish Prime Minister Mariano Rajoy. Juan Medina/Reuters <b>Spain will trigger Article 155 of its constitution over Catalonia this Saturday.</b> The article, dubbed the "nuclear option," will allow Madrid to suspend Catalonia's political autonomy. <b>It has never been invoked before.</b> <b>Tensions between Spain and Catalonia go back centuries.</b> <b>Spain will start suspending Catalonia's autonomy on Saturday, the Prime Minister's office has said</b> .