[5] In 2004, Barnett uncovered Sir Mark Thatcher's involvement in the failed Equatorial Guinea coup to depose the west African state's President Teodoro Obiang.
[8] Barnett's political investigations also include two exposes of how former cabinet ministers offered favours to companies in return for large fees.
[14][15] The documentary was the subject of international press coverage after Oscar-winning actor George Clooney (who had been Nespresso's brand ambassador since 2006) commented on the findings.
[16] Barnett followed up his coffee investigation in 2022 by travelling undercover to Ghana to expose how farms supplying cocoa beans to Cadbury (owned by Mondelez) were using illegal child labour.
[19] His November 2020 investigation "Lockdown Chaos: How the Government Lost Control" uncovered serious failings at one of Britain's largest COVID testing facilities, leading to a probe by Health and Safety Executive for Northern Ireland (HSENI) and a directive to medical firm Randox to address those concerns.
[20] In 2019, Barnett wrote and produced a one-hour documentary on the Great Train Robbery that was based on previously unbroadcast tapes made by one of the gang members, Roger Cordrey.