As Deputy Mayor from June 2004-May 2008, Nicky had responsibility for the environment, strategic planning and children and young people. She helped shape the London Plan and its review, into which she introduced sustainable design and construction. She is producing supplementary planning guidance for all new London developments. Nicky also led efforts to mitigate the impact of Climate Change, a central component of which was the London Climate Change Agency, which aims to reduce London’s CO2 emissions across energy, water, waste and transport.