Gallacher born in Alexandria, Dunbartonshire, was educated at St. Patrick's High School, Dumbarton and worked for Vale of Leven Co-operative Society before World War II.
He served in the Royal Air Force then joined the Scottish Co-operative Wholesale Society (SCWS) in Dumbarton as a trainee in Glasgow.
[2] He went on to work as assistant educational secretary at the Royal Arsenal Co-operative Society in South London, and then moved to be education secretary with the Enfield Highway Co-operative Society.
[1] He was then the Southern Sectional Secretary of the Co-operative Union, leaving for a short while to be labour advisor to the Motor Agents' Association before returning to the Union.
[2] After joining the International Co-operative Alliance as Administrative Officer he became Parliamentary Secretary to the Co-operative Union in 1973, gaining profile and parliamentary support for the movement.