The former electrical engineer has resided at Woolooware Shores Retirement Village at Taren Point since 2006.

But while studying full-time for a masters in international relations, he lived on campus at Bond University in Queensland for a year.

"A lot of people were surprised to see me there,'' he said. "There was 60 years difference between me and the other students.''

After attending the university's open day with his granddaughter, who wanted to enrol, Mr Gardner decided to apply for his chosen course.

"It was tough at my age, but ... I concentrated on doing the job. My family thought it was great,'' he said.

Mr Gardner already had a diploma in electrical engineering under his belt, which he completed in 1948. He then served with the Royal Australian Naval Reserves for 35 years and ran an electrical engineering business for 50 years.

Hitting the books, however, was the pinnacle of his success.

"I did it to keep my mind active,'' he said.

"[But] I'd like nothing more than to be invited by the NSW Parliament to offer my services in some capacity, specifically on matters to do with the environment.''

Mr Gardner, who received a recognition award from the university's faculty of humanities and social sciences for his contribution to university, is now considering doing a doctorate.