Speaker Denison's rule main subject casting vote
Speaker Denison's rule is a constitutional convention established by John Evelyn Denison, who was Speaker of the British House of Commons from 1857 to 1872, regarding how the Speaker decides on their casting vote in the event of a tie in the number of votes cast in a division.
In 1867, when a tie arose on a motion on Fellowships at Trinity College, Dublin, Denison gave his casting vote against the motion, declaring that any decision must be approved by the majority. The rule as subsequently adopted is that the Speaker, in any division upon a bill, should vote to leave a bill in its existing form.The principle is always to vote in favour of further debate, or, where it has been previously decided to have no further debate or in some specific instances, to vote in favour of the status quo. Thus, the Speaker will vote: