Except for a two-year stint as head of finance at a commodity trading house, Ruwayda Redfearn owes her career to Deloitte’s African arm, where she started as an intern before rising to regional head of audit and managing partner for the KwaZulu-Natal region before becoming chair.

To that list Redfearn can add CEO of the global audit and consultancy house’s African division, making her the first female and the fourth consecutive black boss of one of the biggest names in accounting...