Speaker of the House of Commons and the Lord Speaker
The Speaker of the House of Commons chairs debates in the Commons chamber. The holder of this office is an MP who has been elected to be Speaker by other Members of Parliament.
'Mr Speaker' or 'Madam Speaker' is the customary designation on parliamentary matters, otherwise according to his or her rank.
The Lord Speaker is a role elected internally by Members of the House of Lords. Politically impartial, responsibilities of the Lord Speaker include chairing the Lords debating chamber, offering advice on procedure, and acting as an ambassador for the work of the Lords both at home and abroad.
The Lord Speaker is addressed as 'Lord Speaker' (even if female) on parliamentary matters, otherwise according to his or her rank.