Gallagher was one of the first of a succession of All Blacks to switch codes to rugby league.
Gallagher was initially signed by David Ward for Leeds RLFC. He was targeted by opposition players and was badly injured in an alleged spear tackle. He may also have found the tactical differences between the two codes difficult to adjust to, particularly in his favoured full-back position and the move was unsuccessful.
Gallagher found greater success in the less rarefied atmosphere of playing for the club then known as London Crusaders, where his reliable kicking and astute play made a significant contribution over several seasons.