And here's a link, with this about Doreen Bridges near the bottom (my emphasis in bold):

Doreen Bridges told me that Helen Palmer a teacher and historian, had completed her thesis on the English Ballad and was eager to compose ballads with a local flavour so she wrote The Ballad of 1891 and the Ballad of Eureka to commemorate two critical historic events in colonial Australia. Doreen was leader of Unity Singers a Sydney choir among whose members were John Meredith, Alex Hood and Chris Kempster. She had been close friends with Helen Palmer since their days together in the airforce and when she put both ballads to music in early 1951 they became part of the Unity Singers repertoire.