 The episode was heavily based on a moral question posed to the Doctor by Donna : whether to warn the population of Pompeii , or to recuse themselves from the situation . Moran also had to deal with the intensity and sensitivity required when writing about the eruption . Davies and Moran both appreciated Catherine Tate 's performance , and cited Donna 's ability to humanise the Doctor and help him deal with " lose @-@ lose situations " as the reason the Doctor travels with companions . 
