 From 2015 to 2016, Cummings was director of Vote Leave, an organisation which successfully executed the 2016 referendum campaign for Britain's exit from the European Union.After Johnson was appointed prime minister in July 2019, Cummings was appointed as Chief Adviser to the Prime Minister, a new role to replace the position of Downing Street Chief of Staff.Cummings had a contentious relationship with Chancellor Sajid Javid which culminated in Javid's resignation in February 2020 after he refused to comply with Cummings's request to dismiss his special advisers.