He was born in Ballarat to solicitor Joseph Edwin Don and Mary Minnie Cross.
During World War II he served in the Middle East and later the Philippines, attaining the rank of major and being awarded the MBE.
In 1945, Don was elected to the Victorian Legislative Assembly as the Liberal member for Elsternwick, while he was still studying law (he would be admitted as a solicitor in 1954).
A supporter of Thomas Hollway, he was one of the rebels who voted against the McDonald Country Party government in 1952 and served as Minister of Transport and Labour in the seventy-hour ministry that resulted.
Expelled from the Liberal Party, he was defeated as an Electoral Reform League candidate in 1955.