Was the approach proposed for calculating exam grades in summer 2020 fair? Were the grades eventually awarded (after policy changes) fair? What is a fair arrangement for 2021? These questions have been at the heart of debate in the UK in the light of COVID-19. After schools were closed in the spring of 2020 and the decision was made not to proceed with summer exams, it was judged unfair to deny students the grades they needed to progress to the next stage in their lives. The task was to find a fair way to award grades in the absence of exams. The approaches developed in all four parts of the UK--and the Republic of Ireland--were thought by the regulators and Ministers to be the fairest possible, but in the event the grades initially awarded were widely decried as "unfair" and instead all the UK countries switched to awarding Centre Assessed Grades (CAGs). The result was not only significant grade inflation (compared to previous years) but unequal treatment of different subjects and groups of candidates. In this article, we shall briefly recall the conceptual map of "fairness" that we have offered elsewhere and outline received views of assessment fairness before 2020. We shall then discuss five challenges to those received views raised by the COVID-19 experience, particularly in the UK.