“This chapter in medical history is now closed. [John] Herron and I have always denied wrongdoing and were unfairly maligned for many decades. We are now vindicated.”

Dr John Gill, a GP involved in the controversial Chelmsford deep-sleep therapy program more than 40 years ago, was speaking on Monday about the end of his six-year multimillion dollar defamation battle with an ABC journalist.

Both Dr Gill and former psychiatrist John Herron had been among a group of doctors at Sydney’s Chelmsford Private Hospital in the 1970s, where patients had been sedated with barbiturates for up to 14 days for the treatment of a range of issues, including depression, anxiety and addiction.

In the 1980s, the Royal Commission into Mental Health Services, otherwise known as the Chelmsford Royal Commission, subsequently blamed the therapy for the deaths of at least 23 patients.