Former deputy chief whip Sir John Randall announced last night that he will step down from the Government at the next general election.
The Uxbridge and South Ruislip MP has held his seat in the borough since 1997.
He has this morning said that he broke the news about his plan to step down to the Uxbridge Conservative Association last night.
The MP also wrote a letter to Prime Minister David Cameron telling him of his plan to step down at the next election.
It has been speculated that leaving his seat means Mr Randall has opened the door for London Mayor Boris Johnson to make a return to the Commons in 2015.
More on this story: Mr Randall says "whoever becomes MP would have my full support"