Deborah Lat year you posted a request re the earlist Diggins in Australia. My great grandfather Precival Goerge Laexander Diggins was born in Gaffneys Creek Victoria in 1882. His oldest sibling William Robert Diggins was also born in Gaffneys Creek in 1865.
This indicates to me that my Great Great Grandfather John Emmauel Diggins arriverd in Australia prior to 1865. John Emmauel was born in Rattery, Devon, England in 1839 and died in Gaffneys Creek in 1902.