"The office of Speaker is almost as ancient as Parliament itself. It emerged in the Middle Ages when the Commons - the ordinary people - of England needed a spokesman in their dealings with the King, someone who would voice their grievances and present their petitions. This was by no means a safe or easy thing to do at that time, and potential spokesman generally had to be pressured into accepting the responsibility."
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Source : John Allen Fraser (1993). “The House of Commons at Work”, Montréal : Éditions de la Chenelière