He was born in
Melbourne to saddler John Dinwoodie and Janet,
née McFarlane. He was sent to a private tutor in England before travelling to
Rockhampton with the intention to become a pastoralist. He instead became a gold miner at the
Calliope gold rush and moved to
Gympie in 1867, where he became a magistrate under the name John Hamilton. He also practiced as a doctor despite his lack of qualifications, and in 1877 was a surgeon to the hospital at the
Hodgkinson gold rush, where he attracted publicity with a public dispute with the local warden and a successful defamation case after allegations that he seduced the daughter of a friend of the local editor. ==Politics==