The PSA is one of the oldest and most substantial examples of public sector and white-collar unionism, and its female activists played a leading role in the equal pay movement from 1914. Despite this, it has attracted little attention from historians. Sheldon's solitary article on the formation of the PSA characterises it as a 'middle-class' union, on the basis of public servants' social position, industrial conservatism, limited links with the labour movement generally and the PSA's non-political stance. However, the eschewing of strikes and overt political attachments were as much the product of the unusual legal and political position public servants found themselves in. Furthermore, on a material basis, whilst many white-collar public servants did enjoy a better position than ordinary workers, about half clearly earned working-class levels of pay. The circumstances of the 1920s and 1930s also brought the PSA closer to the mainstream of the labour movement, in terms of solidarity of outlook and a radicalisation of its world view. Its experience was a precursor of wider changes in white-collar unionism in the 1960s and 1970s.