On 25th June 2018, the UK Parliament voted to approve the "Airports National Policy Statement: new runway capacity and infrastructure at airports in the South East of England" as presented to Parliament pursuant to Section 9(8) of the Planning Act 2008.
The document outlines Government policy relating to airport expansion in the south east of England with a third runway at Heathrow being its favoured option.
Opponents of the project have six weeks from the 25th to challenge the scheme in the High Court via judicial review.
It is up to Heathrow Airport Limited (or a third party), to apply for a development consent order for the project to proceed, depending on the result of any court proceedings.
Construction is scheduled to begin in 2021 with the runway opening in 2026.
The policy document can be found here
Further information on the planning process can be found here.