This historical exploration of the development of the academic workforce in the UK and France was triggered by the observation of significant similarities in contemporary debates on casualisation, and segmentation despite their distinctive HE systems. We develop a quantitative history of academic staff to understand why the differences in the two HE systems are not as significant in respect to labour market and working conditions. The new data show that connected processes of casualisation, professional segmentation, and sectorial differentiation are used to manage tensions between massification and staff recruitment in both countries, in a context of declining and increasingly unequal distribution of resources, producing inequalities within institutions, as within the profession itself. The reorganisation of the academic workforce during three periods of growth of HE systems under traditional, Fordist and managerial influences has incrementally produced three groups of permanent, casualised, and precarised staff and a dual academic labour market.