On his return, Campbell rejoined the railways, and was elected as branch secretary in the NUR.[3] He held a succession of increasingly senior positions in the union, eventually becoming a full-time organiser, then the chief organiser for Ireland, and assistant general secretary.[2]
In 1953, Campbell was elected as general secretary of the NUR, and he was also elected onto the General Council of the Trades Union Congress. While in office, he visited the Soviet Union,[2] with Tom Hollywood and four other union representatives. Just outside Leningrad, the car in which he and Hollywood were travelling was hit by a bus, and both were killed.[4] Campbell was 62.