We investigate the relationship between social origin, postgraduate degree attainment, and occupational outcomes across five British age‐group cohorts. We use recently‐available UK Labour Force Survey data to conduct a series of logistic regressions of postgraduate (masters or doctorate) degree attainment among those with first degrees, with controls for measures of degree classification, degree subject, age, gender, ethnicity and national origin. We find a marked strengthening of the effect of class origin on degree‐ and occupational attainment across age cohorts. While for older generations there is little or no difference by class origin in the rates at which first‐degree graduates attain postgraduate degrees, those with working‐class‐origins in the youngest age‐group are only about 28 per cent as likely to obtain a postgraduate degree when compared with their peers from privileged origins. Moreover, social origin matters more for occupational destination, even among those with postgraduate degrees, for those in younger age groups. These findings demonstrate the newly important, and increasing, role of postgraduate degrees in reproducing socio‐economic inequality in the wake of the substantial expansion of undergraduate and postgraduate education. Our findings lend some support to the Maximally Maintained Inequality thesis, suggesting that gains in equality of access to first‐degrees are indeed at risk from postgraduate expansion.