Born in Prestwich, Southern was educated at Stand Grammar School. He was interested in the co-operative movement from an early age, joining the Co-operative Wholesale Society (CWS) in 1923. He studied at the Co-operative College, and from 1929 worked for the Co-operative Union. In his spare time, he completed a degree in commerce with the University of Manchester.
In 1946, Southern was appointed as assistant general secretary of the Co-operative Union, and he was promoted to general secretary in 1950. He remained in this post until his retirement, in 1972, also serving as a vice-president of the International Co-operative Alliance and as president of the 1969 Co-operative Congress.
Southern devoted much of his spare time to the Stand Unitarian Chapel, serving as secretary of its trustees, and as superintendent of its Sunday school. He was also secretary of the Besses o' th' Barn Band Company, a brass band, and was active in the Radcliffe Literary Society and Camera Club. He was made a Commander of the Order of the British Empire in 1953, and was knighted in the 1970 New Year Honours.
- England & Wales, Civil Registration Death Index, 1916-2007
- "Former UK Co-op chief dies aged 92". Lancashire Telegraph. 1 October 1999. Retrieved 10 March 2018.
|Non-profit organization positions|
| General Secretary of the Co-operative Union