Voters whose first preference was for an eliminated candidate, but who put one of the remaining two candidates as their second choice, will then have their second preferences counted.
Those second preferences are used to top up the totals of the remaining candidates, and whoever has the highest total wins.
The incumbent, Conservative James Palmer, won in 2017, but his lead narrowed when the second preferences were counted, from 29,000 votes to 21,600.
He secured 38 per cent of the vote in the first round, and 56.9 per cent in the second.
The Lib Dems secured 23.5 per cent in the first round, coming second.
Their vote share then increased to 43.1 per cent when second preference votes were counted.
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