The move means compulsory redundancy for previous chief executive Jo Turton and voluntary redundancy for director of governance Ian Young.
In her most recent role, Angie Ridgwell has been director general, corporate services at the Department for Business, Energy and Industrial Strategy, since October 2016.
Before joining central government, Angie was strategic director for corporate services and strategic director of organisational design for Bristol City Council and chief executive of Thurrock Council. She has had a career working with a range of local authorities, government agencies and the private sector.
"This is a crucial time for the county council, as we face an unprecedented financial challenge. Our restructure of senior management recognises that challenge and required us to find an exceptional candidate, someone who not only has highly developed skills as a visionary leader, but also has the necessary professional finance qualifications and experience of managing the finances of a major organisation.
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