Alfred arrived in South Australia as an officer on the brig Rapid in August 1836, his wife-to-be Priscilla aboard John Renwick in February 1837.
He was a member of a consortium with brother W. Pitt Barker and brothers-in-law Donald Maclean and Hugh Chambers that purchased Queensland cattle properties Gunnadorah, Gunnadorah West, Koraggarak, Lake Colless, Yungerah, Wombadullah, Owthorpe No.1 in 1882; Godesberg, Annie Jo Jo, Bonn, Denman, Gap, Galvin, Phipps, Stop, Theirs, and Youngwoman in 1883; Winbin, Winbin North and Tabletop in 1882; Colac, Derremut, Geneva in 1883; and consolidated them as Comongin holding in 1888; In 1890, after the death of his wife from tuberculosis, Donald Maclean and his daughter Mary Stewart Maclean moved to Comongin to live.
John Barker and Agnes May Chambers (who had inherited her father's share) sold their interest to the new company for £88,360.
A. Simpson, a board member of the South Australian Chamber of Manufactures, whose president was Wallace Bruce and secretary was H. E. Winterbottom, and an adherent of the Church of England and a member of St. Cuthbert's Church, Prospect, whose rector was the Rev.
He was partner with James Hill, of Clare in several horses including The Greek, winner in 1909 of the South Australian Derby.
He was elected to committee of the South Australian Jockey Club in 1894, and was appointed chairman in May 1909, succeeding Sir Richard Baker.
He served in both capacities until July 1924, when he resigned from the board, and was made a life member of the club.