In 1946 Dunstan joined The Herald and Weekly Times Ltd, publishers of The Sun News-Pictorial and The Herald (since merged as the Herald Sun). He was Foreign Correspondent for the H&WT with posts in New York (1949—52) and London (1952—54). This period was followed by a position with The Courier-Mail for which he wrote a column ‘Day by Day’. He returned to Melbourne and from 1958 to 1978 contributed a daily column, ‘A Place in the Sun’ for The Sun News-Pictorial, the city’s largest circulating daily newspaper. During these years his popularity grew and he became a Melbourne institution. From 1962 he wrote regularly for the Sydney based weekly magazine The Bulletin under the pseudonym of Batman (after the city’s controversial founder, John Batman) and for the travel magazine Walkabout Walkabout magazine. He was United States West Coast Correspondent (1979—82) for the H&WT, afterwards a regular columnist and occasional contributor to The Age.

He has published a quartet on Australian character: Wowsers (1968), Knockers (1972), Sports (1973) and Ratbags (1979) and many works of history on popular subjects ranging from wine to sport to retailing, and including an unfashionably critical study of the Australian outlaw Ned Kelly, Saint Ned (1980). His pioneering works of Australian sports history include The Paddock That Grew (1962) on the Melbourne Cricket Ground, which has now seen several editions and updates. He has also written an autobiography, No Brains at All (1990). Recent publications have been The Melbourne I Remember (2004) and Moonee Ponds to Broadway (2006), a study of his friend and fellow Melburnian, the satirist Barry Humphries.

An enthusiastic commuter and recreational cyclist, he was the founding president of the Bicycle Institute of Victoria (1974—78) and from 1967 founding secretary of The Anti-Football League, a tongue-in-cheek organisation that pokes fun at the Australian rules football obsession. Whilst living on Victoria’s Mornington Peninsula he was an enthusiastic grower and maker of pinot noir wine. He was awarded an OAM in 2002. On 26 May 2009 he became Patron of the Prahran Mechanics' Institute.