The most prominent duty of Black Rod is the summoning of the members of the House of Commons to hear a speech from the throne or the royal assent given to bills.
On such occasions the House of Commons closes its doors at Black Rod’s approach, whereupon he or she must knock three times before being admitted. The origin of this curious ceremony dates from the indignation of the lower house at the famous attempt of Charles I to arrest John Hampden, John Pym, and three other members of the House of Commons in 1642.