Returning home in 1952, she began work at J. Lyons and Co. as a temporary clerical worker, a job she reluctantly accepted while searching for a better alternative.
[10] Coombs' mathematical skills soon allowed her to transfer from the Ice Cream Sales department to the Statistical Office, where she heard that the division working on LEO computers[11] had been looking to hire additional programmers.
[12][2] The selection process, devised by Thomas Raymond Thompson, was conducted as a "computer appreciation course", which consisted of a gruelling week of daytime lectures and evening written assignments designed to test the candidates' aptitude for computer work.
[14] Coombs also worked on programs for early LEO customers such as the Met Office, the British Army and the Inland Revenue.
She spent most of her time as a supervisor, checking for logical and syntactical errors in the programs that other people wrote.
She developed programs for internal company use and for outside clients as another portion of the business computing service offered by the firm.
[18] She briefly taught a computer programming course at Princess Marina Centre at Seer Green for disabled residents.
Coombs died on 28 February 2022, at the age of 93, survived by her three children, three grandchildren, and her sister, Ruth.