Brett was a Senator for Queensland from 1999 to 2015, serving in the Howard and Abbott ministries. He then served as Australia's Ambassador to the Netherlands and Permanent Representative to the Organisation for the Prohibition of Chemical Weapons.
He is currently an Adjunct Professor in the School of Justice at QUT and serves on the Griffith University Council. Until late 2024, he was Chair of the Council of the National Library of Australia.
He has recently published two best-selling books, “Wizards of Oz: How Oliphant and Florey helped win the war and shape the modern world”, NewSouth, Sydney, 2022 and “Saving Lieutenant Kennedy: the Heroic story of the Australian who helped rescue JFK”, NewSouth, Sydney, 2023.