Boris Johnson has made his final Commons appearance after announcing he is stepping down as Tory MP for Henley.
The move, one of the London mayor's pre-election pledges, will spark a by-election in the Oxfordshire seat - one of the safest in the country.
Oxfordshire councillor John Howell will be the Conservative candidate.
Labour's candidate is Richard McKenzie, and the Lib Dems' is Stephen Kearney. The Greens have chosen Mark Stevenson and UKIP have selected Chris Adams.
Mr Johnson received loud cheers from MPs on all sides as he rose to make his final Commons appearance at prime minister's questions.
He began by thanking Speaker Michael Martin for his "kindness" over the years before drawing MPs' attention to his own early achievements in City Hall.
I am sure the whole House is going to miss the contributions you have made
Prime Minister Gordon Brown
"Can I use my last few seconds in this great cockpit of our nation, Mr Speaker, to ask the prime minister to join me in congratulating the London authorities in successfully implementing the ban on alcohol on tubes and buses.
"And in doubling the 'Safer Transport' teams, so that we will have more uniformed people on the buses than any time in the last 25 years."
Mr Johnson was cut short by Mr Martin, who rebuked "the lord mayor" for asking too many "supplementary" questions.
Prime Minister Gordon Brown told Mr Johnson: "I am sure the whole house is going to miss the contributions you have made.
"Not only the contributions in speech, but in writing which have been actually more significant over the last few years."
Mr Brown said he welcomed the ban on alcohol on the underground - but he said the extra officers on London's streets were partly down to the "previous mayor" and decisions taken by the Labour government.
Mr Johnson used his first news conference as London mayor to announce his retirement from the House of Commons.
He said it would be difficult for him to leave the constituency where he has been MP since succeeding former Deputy Prime Minister Michael Heseltine in 2001, with a majority of 8,458.
"It will be a huge wrench for me to leave Henley, which is of course full of the nicest, kindest and most wonderful people in the world outside London, but I do so, of course, because this job here in City Hall is simply too big and it is growing all the time," he said.
The most likely date for the by-election is thought to be 26 June.
Mr Johnson was re-elected in 2005 with an improved majority of 12,793 and a 53% share of the vote.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.