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Now he and his doctoral students are working on a drug that targets late stage bowel and bladder cancer but does not harm normal cells.
''The drug is promising so we are trying to find a company that might be interested in taking the work further,'' Professor Williams said.
''It is just in the early stages and drug development takes a long time.''
It is a different world from crutching and working a wool press for three months a year.
Prof Williams was born in Mosgiel and went to Taieri High School (now Taieri College).
His parents had a lifestyle block and his father Ray taught him to shear.
''I was never good enough to be a shearer but did do a bit of crutching and worked in the yards and on the wool press.''
He also spent time working on his first wife Vivian's father's farm in Waitahuna.
After graduating with a Bachelor of Science (with honours) in Microbiology in 1973, he received his PhD in 1976.
He moved to London to work at the National Institute for Medical Research.
Later he went to Toronto in 1980 to work at the Hospital for Sick Children and the University of Toronto, and then to the Lerne Research Institute at the Cleveland Clinic, Ohio, until 2005.
Prof Williams was appointed director of Monash Institute of Medical Research in Melbourne in 2006, and when it merged with the Prince Henry Institute in 2014, he became chief executive and director of the new Hudson Institute of Medical Research.
Prof Williams has been involved in various cancer-related research projects, received several awards, honours and fellowships, and is a director on the Dunedin company Pacific Edge Ltd, which provides bladder cancer diagnostic tools.
Now nearly 70, he intends to retire in a few months, and he and wife Lynda Power are thinking of returning permanently to New Zealand where they have a holiday home in Clyde, the McFelin Ridge vineyard in Lowburn, and where the fishing is good.
However, before that happens, he has been asked to be a consultant at a research facility in Riyadh, Saudi Arabia, as well as the Cleveland Clinic, Ohio.
Prof Williams said he had not given up the rural lifestyle entirely as they had a 45ha property near Melbourne where they raised and fattened cattle.
''It is a hobby farm with some sheep to keep the grass down and it pays the rates.''
They sell the fruit from their vineyard to Mt Difficulty, which uses it in its Roaring Meg pinot noir.
Mt Difficulty also produces the McFelin Ridge chardonnay.
''I don't have enough time to be hands on [at the vineyard] but I do a bit of native planting and bush cutting,'' he said.
They have three children between them, including Mark Williams who has a visual effects business and has done work for Star Wars.
Roscoe Power runs two businesses in Melbourne, and Sarah Power is a pharmacy technician there as well.