Autopsy: The Last Hours of Cory Monteith aired last night on on Channel 5 and revealed the cause of the young actors death.
The Glee star died from a combination of alcohol and heroin in his system.
Cory was found dead at a hotel in Vancouver, Canada on July 13 2013 aged just 31 after struggling with substance abuse for most of his adult life.
The final coroner's report said, "Mixed drug toxicity, involving intravenous heroin use combined with the ingestion of alcohol."
Speaking in the documentary, Dr. Payne-James said: "Cory was tragically unaware that his central nervous systems was already compromised because of the amount of alcohol he had consumed throughout the evening.
"Within seconds after injecting the heroin the effects go these two drugs combined to suppress his ability to breath. As his breathing slows his heart has a much more difficult time pumping oxygen around his blood.
"Ultimately it was the alcohol and heroin in combination that killed him and not the heroin in isolation'
