 In 2007, Thornton became Chief Constable of Thames Valley Police.Following an inspection by Her Majesty's Inspectorate of Constabulary in 2010, Thornton accepted that the number of crimes being solved by the force had fallen too low and needed to increase from 14%, which was then the lowest in the country.On 1 December 2014, it was announced that Thornton would leave Thames Valley Police to become the Chair of the National Police Chiefs' Council, (NPCC) effectively taking over from Sir Hugh Orde.