[1][2][3] Brearley worked in Prime Minister Tony Blair’s strategy unit within 10 Downing Street from 2002 to 2006.
[2] He then transferred to work for the Department for Environment, Food and Rural Affairs while David Miliband was Secretary of State, where Brearley was tasked with setting up the Office of Climate Change.
[2] He then moved to the Department of Energy and Climate Change where he was director of electricity markets and networks.
[4] After leaving the UK civil service, Brearley ran a consultancy working on projects in the energy industry including market reforms in India.
[4][1] He then joined Ofgem, working as executive director for systems and networks, and in February 2020 was appointed CEO where he is paid over £300,000 per year.