Comedian Alistair McGowan explains why he is attending the rally.
Zac Goldsmith MP joined the Mayor and hundreds of others in Barnes at a rally against Heathrow's third runway.
Richmond Council, which serves residents who live under the airport's flight path, is currently leading a referendum on the future of Heathrow.
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.