His father was the surgeon John Baptist Austin II: a family tradition held that he had been called to attend in 1797 after Mary Lamb's fatal stabbing of her mother Elizabeth.

Going into business himself in London as a surgeon, he attracted the attention of George Birkbeck, who helped him find work as a lecturer.

He sent them a South Australian newspaper, which had a direct bearing on Harry Congreve's decision to emigrate later himself.

[10][11][12] Accompanied by Isaac Todhunter, Austin moved his school to Peckham, then a village south of London, around 1835.

[18] A service to mark the departure of the Austin family was held on 14 September 1843 in the Albany Chapel, Camberwell, led by the Rev.

[21][22] With Alexander Lang Elder (his future son-in-law) as agent, he bought land at Bugle Ranges from Frederick Harrison, in an area first granted to the Davenport family.

[24] From 1844 he had regular preaching stations: at Echunga in Walter Duffield's house; at Mount Barker in Denman McFarlane's barn; at Strathalbyn, where a church was built in 1844 and he held services every two weeks; and at Bugle Range's, at a place later called Zion's Hill.

[29] Austin in 1841 married at Finsbury Chapel, with Alexander Fletcher officiating, Matilda Lashbrooke.

She was the daughter of the late John Lashbrooke, of Trinity Square Gardens, Tower Hill.