On Monday 25 June 2018 the House of Commons voted, by 415 to 119 votes, in favour of the Airports National Policy Statement. This means that a formal planning application for the proposed north-west runway (the third runway) can be submitted. Building works could start in 2021 and the runway become operational by 2026.
The press story can be found at: https://www.gov.uk/government/news/government-sets-out-next-steps-for-heathrow-expansion
The Airports National Policy Statement can be found at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/714106/airports-nps-new-runway-capacity-and-infrastructure-at-airports-in-the-south-east-of-england-web-version.pdf