A coalition of councils has teamed up and hit the government with legal papers for unlawfully supporting the expansion of Heathrow.
And while the councils all made their intentions clear a while back, it does prove a headache for Theresa May as her own local council, the Royal Borough of Windsor and Maidenhead, is involved in the action.
The submission to the High Court wants a judicial review of the decision announced by transport secretary Chris Grayling to support the expansion, arguing that the government failed to recognise the development's air quality impact, which the councils say will breach laws. They also say the government has acted contrary to the councils' expectation it would honour its "repeated promises" not to expand Heathrow.
Cllr Simon Dudley, leader of the Royal Borough of Windsor and Maidenhead said: "The Royal Borough has been very consistent in saying it will hold government to account for its decision and seek to protect our residents from the public health risks of an expanded Heathrow Airport."
Should the judicial review go ahead and succeed in the High Court, the decision to proceed with the runway could be overturned.
Cllr Ray Puddifoot, leader of the Hillingdon council, said:
The government has stubbornly refused to accept that it is breaking the law on the very important issue of air quality in relation to Heathrow.
Therefore, this council, together with the London boroughs of Wandsworth and Richmond upon Thames, the Royal Borough of Windsor and Maidenhead, Greenpeace and a Hillingdon resident, have had no option other than to issue judicial review proceedings in the High Court.
Last month, the mayor of London, Sadiq Khan said he would back a legal challenge against Heathrow expansion and had directed Transport for London (TfL) to provide advice and assistance to the affected councils.
A Heathrow spokesman said on the news that the mayor was supporting the expected legal challenge: “The Airports Commission’s detailed work represents a solid foundation to support a government decision for the third runway, and we are confident that any legal challenge would be unsuccessful and would not affect the timeline for delivering a third runway. We want to work with the mayor to ensure that Heathrow expansion helps London thrive as a global hub for talent, tourism and trade.”