He married Mary Cook Woolmer in 1828, thus breaking probationary conditions for the ministry leading him to teaching in a Methodist day school in Greater Queen Street, London.

[3] The Colonial Office in England appointed him as assistant Protector of Aborigines, and he and his wife and six sons sailed for Sydney.

Robinson appointed Parker to the northwest or Loddon District in March, but he did not start his protectorate until September 1839.

The Protector's duties included to safeguard aborigines from "encroachments on their property, and from acts of cruelty, of oppression or injustice" and a longer-term goal of "civilising the natives".

[1] Parker initially established his base at Jackson's Creek near Sunbury, which was not close enough to the aboriginal nations of his protectorate.

Parker suggested to Robinson and to Governor Gipps that protectorate stations be established within each district to concentrate aboriginals in one area and provide for their needs and so reduce frontier conflict.

[1] Parker also attempted to prosecute those European settlers who had killed aborigines including Henry Monro and his employees for killings in January 1840 and William Jenkins, William Martin, John Remington, Edward Collins, Robert Morrison for the murder of Gondiurmin in February 1841.

[5] While chiefly remembered for his work as Assistant Protector, Parker was a leading layman and preacher in the Port Philip colony's Methodist community.