For many practical purposes, it is often assumed that the quality of a marker is directly related to their seniority. At its extreme, the assumption is that the most senior marker (the Principal Examiner) is always right even in cases where large numbers of junior markers have a collectively different opinion regarding the mark that should be awarded to a given script. To investigate this assumption, this article compares the predictive value of marks provided by the most senior marker to those made by simply taking the mean mark awarded by many junior markers. Predictive value was estimated via the correlation of the scores assigned to scripts with the overall achievement of the same candidates in other exam papers taken within the same month. By looking at the relative predictive value of the two different sources of marks, we can begin to make some inferences about the extent to which senior markers are genuinely more accurate than their junior colleagues.