[2] Bannon began her career as a ward sister of St Thomas' Hospital and in 1918 received a Cowdray scholarship from the College of Nursing to study nurse's teaching at King's College of Household and Social Science after completing the one-year course, the dean requested that she be allowed to continue for an additional year to study public health.

[2] As Matron-in-Chief of the service, her job was to direct and supervise the 11,000 nurses who worked at the seventy-five various facilities, including asylums, hospitals, sanatoria and schools, which made up the LCC network.

[4] She presided over County Hall meetings of matrons, evaluating staff inspections and had to balance daily operations activities with strategic planning for the LCC.

[6] Transitioning general training to a four-year study, Bannon was able to shift the LCC from the volunteer type service that had previously existed in England to a public-funded profession.

[4] As World War II approached, Bannon organized the Emergency Medical Service and incorporated the LCC hospitals into the Civil Defense sectors into which London had been divided.