This expression can be found on page 6 of the novel where Mr Audu was described to be "a bunch of biting humour". He complained about how the MD was "a witch and wizard rolled into one" because of the way she was able to find a way to offset the cost from the Boarding House discount by increasing the Excursion fees. This is one of the examples that illustrate how Mr Audu is sarcastic and full of sharp, critical wit.