John Bercow is standing down as Commons Speaker after 10 years in the chair.
A replacement for Mr Bercow will be elected in due course – with favourites including his deputy Sir Lindsay Hoyle and former deputy prime minister Harriet Harman.
He will also resign as MP for Buckingham – a seat he has held for 22 years – which will be hotly contested in the general election this December.
Mr Bercow announced his intention to stand down from the influential position in September, saying the timing was the “least disruptive and most democratic course of action”.
He would have relinquished the role sooner if MPs had supported Boris Johnson’s initial attempt for an early general election in September.
The 56-year-old entered Parliament in 1997 and held several shadow ministerial positions before taking the Speaker’s chair on June 22 2009, promising to serve “no more than nine years in total”.
He abandoned that commitment ahead of the 2017 snap election, but allegations of bullying by former members of his staff, denied by the Speaker, led to fresh calls for him to quit.
In recent months he has also come under fire for a series of controversial rulings in the chamber which were widely considered to favour Remain supporters.
The contest to replace Mr Bercow will take place via a secret ballot, with a result announced on the same day as voting.