During this period he was active in university acting and was hired as an extra in BBC series The Goodies, Monty Python's Flying Circus and Doctor Who.

[3][2] He joined the Australian Broadcasting Corporation (ABC) Science Unit in 1972 where, after several years in background production and interviewing for the Insight program, he hosted Innovations in early 1974,[4] Investigations (2-hour format) from 6 November 1974.

[2] He is a good friend of fellow ABC presenter, Norman Swan, a qualified medical doctor, who intervened to help save his life when he suffered a cardiac arrest in 1988.

[3] As of 2022[update] Williams is in a long-term relationship with Jonica Newby,[3] a former presenter on ABC Television's Catalyst science journalism program.

Williams underwent chemotherapy for colorectal cancer in 2014 and 2015; at one point he was hospitalised for five weeks but continued to make The Science Show from his hospital bed.