R (on the application of ClientEarth) v Secretary of State for the Environment, Food and Rural Affairs [2015] UKSC 28, [2015] All ER (D) 221 (Apr)
During the course of proceedings arising out of the admitted and ongoing failure by the UK to secure compliance in certain zones with the limits for nitrogen dioxide levels set by Directive (EC) 2008/50 of the European Parliament and of the Council (on ambient air quality and cleaner air for Europe), the Supreme Court made a mandatory order requiring the defendant secretary of state to prepare new air quality plans under Art 23(1) of the Directive, in accordance with a defined timetable, to end with delivery of the revised plans to the European Commission not later than 31 December 2015.