He went to Bendigo during the Victorian gold rush, but returned to South Australia in 1853, and having had some success, established the Vauxhall Tea Company, which he operated for 44 years.
Sellar was a well-known Congregationalist, attending Thomas Quinton Stow's church from his arrival, and occupied a number of senior positions in the voluntary militia force.
[2][3][4][5] Sellar was one of the founders of the National Reform Association, and when that wound up, was the first president of the Adelaide Democratic Club.
He was eventually successful in being elected as a Town of Adelaide councillor for Young Ward, serving from 1891 to 1903 and from 1904 to 1906, being defeated for the final time in the same month he died.
[2][3][4][5] He died at his home, "St Heliers", on South Terrace, while in office in 1906, after being ill for several weeks, at the age of 76.