[3] His father worked as a clerk for the Great Western Railway; the family lived in "austerity" in "a small terraced house with an outside toilet and 'no carpet, just coconut matting'"- it was only after his paternal grandfather died, leaving £40, that the family gained hot water and a bathroom, having previously shared the water used in an old zinc tub placed in front of the fire once a week.
On leaving Port Talbot County School in 1940 at the age of 14, when his father died, he started work in the laboratory at a metalworks and continued his education by taking evening classes at Swansea Technical College.
Jenkins had early involvement in his trade union, the Association of Scientific Workers (AScW), and become a lay official in 1944, when he was elected as secretary of his branch.
In 1946, at the age of 20, he left Port Talbot to become a full-time official at the Birmingham office of the Association of Supervisory Staff, Executives and Technicians (ASSET), where he was appointed assistant divisional secretary.
In 1988, shortly after ASTMS merged with TASS (the Technical, Administrative and Supervisory Section) to form MSF (Manufacturing, Science and Finance), Jenkins unexpectedly announced his retirement.
[9][10] Upon retiring, Jenkins- by then having divorced- went to Tasmania with "a beautiful girl friend" to run a hotel and restaurant, which proved "a foolish decision" as "within a year, the business and the affair collapsed" leaving him "back in London trying to pick up the threads of his life."