Boris Johnson is set to hold a press conference later setting out his preferred options for a new airport in the south east. Boris announced yesterday he was moving away from the idea of an airport on an island in the Thames Estuary.
He told the Sunday Times he preferred plans for a four-runway airport on the Isle of Grain, an idea originally conceived by the architect Sir Norman Foster.
Comedian Alistair McGowan explains why he is attending the rally.
Boris Johnson today urged the Government to resist the "great Moloch of aviation capacity" and rule out a third runway at Heathrow before the next election. At a rally against expansion, he said it would be "totally nuts" for the Conservatives to go to the polls without having buried the idea.
He said: "It is just too difficult to deliver - 15 years at least it would take to bring about.
"Above all you would be inflicting noise pollution not just on west London but on huge parts of London that don't even know they are going to be affected.
"That is not the right way forward for the greatest city on earth."The protest in Barnes, west London, attracted around 1,000 residents who live under the airport's flight path.
Mayor of London Boris Johnson will today attend a cross-party rally against the highly controversial proposal to build a third runway at Heathrow airport.
Organisers say they expect thousands to turn out for the protest in Barnes, west London, to voice their opposition to expansion of the travel hub.
The Mayor has previously accused David Cameron of kicking the matter "into the long grass" by delaying an independent report on the future of aviation until after the next election.
He favours a new "Boris island" airport in the Thames Estuary or possible expansion at Stansted.
Former transport secretary Justine Greening is expected to make her first speech on Heathrow since she was moved to international development in September's Cabinet reshuffle amid speculation that it was due to her stance on the issue.
Boris Johnson, Zac Goldsmith and a number of MPs will attend a rally in Richmond against the expansion of Heathrow Airport later today.
Traffic was brought to a standstill in Hampshire as London Mayor Boris Johnson went shopping. He popped into a supermarket, not to get his weekly shop, but to pick up votes. There's just a week to go until the Eastleigh by-election. Political Correspondent Phil Hornby reports.
The Mayor of London Boris Johnson has been out on the campaign trail at a supermarket, helping the Conservatives' Eastleigh by-election candidate.
Boris Johnson is in Eastleigh on the by-election campaign trail. The Mayor of London is the latest in a line of heavyweight Conservatives supporting the Tory candidate Maria Hutchings. Read more about the Eastleigh by-election by clicking here.
The other candidates are: Labour - John O'Farrell; Liberal Democrats - Mike Thornton; UK Independence Party - Diane James; National Health Action - Iain MacLennan; Peace Party - Jim Duggan; Independent - Danny Stupple; English Democrats - Mike Walters ...
Monster Raving Loony Party - Alan Hope; Wessex Regionalists - Colin Bex; Elvis Loves Pets - David Bishop; The Beer, Baccy and Crumpet Party - Ray Hall; Christian Party - Kevin Milburn; Trade Unionists and Socialists - Daz Procter.
He thinks it's a good idea and he is sticking with it. Despite a new report suggesting that it would cost the tax payer billions to build a floating airport hub in the middle of the Thames Estuary, Lord Mayor Boris Johnson has remained unrelenting in his support for the project.
He brushed over suggestions that expansion at Stansted might now be his preferred option for development of British airport capacity, but conceded it's a possibility. More later.