Diana Wynne Jones said this quote

“ Slender Youth. A tour companion who may be either a lost prince or a girl/princess in disguise. In the latter case it is tactful to pretend you think she is a boy. She/he will be ignorant, hasty and shy, and will need hauling out of trouble quite a lot. But she/he will grow up in the course of the Tour. In fact she/he will be the only Companion who will change in any way. Quite often, she/he will soon exhibit a very useful talent for magic and end up by hauling everyone else out of trouble. But this will not be until midway through your second brochure. ”