After marriage to a physicist, Derek Shirley, in 1962, Shirley founded, with a capital of £6, the software company Freelance Programmers, (later FI, then Xansa, since acquired by Steria and now part of the Sopra Steria Group). Having experienced sexism in her workplace, "being fondled, being pushed against the wall", she wanted to create job opportunities for women with dependents, and predominantly employed women, with only three male programmers in the first 300 staff, until the Sex Discrimination Act 1975 made that practice illegal. She also adopted the name "Steve" to help her in the male-dominated business world, given that company letters signed using her real name were not responded to. Her team's projects included programming Concorde's black box flight recorder.