ClientEarth is an environmental lawyers organisation that brought the case to the Supreme Court. It comes after the Court of Appeal declined an application for judicial review of the Government's plans to improve air quality.
Today Lord Carnwath JSC backed ClientEarth's case, ruling the Government is breaching article 13 of the EU Air Quality Directive.
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Pictures of today's events unfolding following a major security incident at the Houses of Parliament.
At least two people have died after a knifeman brought terror to the heart of Westminster.
The Cobra committee brings together government ministers with senior officials of the emergency services and security agencies.