In contrast to Rose and Mickey, Martha is middle-class and university-educated; for Michael and Margaret Rustin of the University of East London, Mickey's constant struggle for respect and recognition from the Doctor in the first two series was a "subtle exploration ... of the dynamics of multi-ethnic life in contemporary Britain". The Rustins argue that in introducing Martha the series "catches hold" of the fact "that black women have in general been more successful educationally and professionally than black men in contemporary Britain." As a black time traveller, the series' writers have used the character's presence as a means of injecting social commentary, tackling social issues such as racism in both bygone eras as well as the present day.