 Cowell left school at the age of 16 to join General Aircraft Limited as an apprentice aircraft engineer, but soon left to join the Royal Air Force, becoming an acting pilot officer on probation on 4 August 1936; Cowell began pilot-training, but was discharged because of air-sickness.In 1936, Cowell began studying engineering at University College London.Also in that year, she began motor-racing, winning her class at the Land's End Speed Trial in a Riley.