Mike Cutler, 63, was first diagnosed with cancer in 2009. He was given a new liver and the all-clear, but last year new cancerous cells were found attacking his new organ.
That's when the grandfather-of-nine, who hails from East Sussex, searched for a cure on the internet and discovered a YouTube video promoting the use of cannabis oil.
Cutler said: "Finding out I could die was terrible. All I had in those dark days was my laptop, and that's when I began searching for something else that could help me. I couldn't accept I was going to die."
He bought the class B drug from a dealer, made his tablets from the oil, and claims that after three days of taking one capsule a day, his excruciating pain disappeared.
He has since started growing his own cannabis plant to keep up a steady supply of the medication.
Cutler described himself as a "normal family man, not a druggie", but was shocked to find that cannabis helped cure his serious illness.
When Cutler went for a biopsy in May this year at the Royal Free Hospital, London, he claims the doctors told him the new cancerous cells had disappeared.
A spokeswoman from the hospital confirmed that he had not received any cancer treatment since his transplant in 2009.
Cutler is now campaigning for changes in the law to legally allow the oil and other forms of cannabis to be used medicinally to treat other people.
In research published last week, scientists at the University of East Anglia found the main psychoactive ingredient in cannabis (tetrahydrocannabinol) had been found to limit the growth of cancerous cells.
Charities are also investing more time into researching the benefits of cannabis as a medical drug. Dr Kat Arney, Cancer Research UK's science communications manager, said: "This could potentially lead to more effective treatments for cancer in the future, but there's still no good data from clinical trials to show that cannabis or cannabinoids can safely and effectively treat cancer in patients at the moment."