JK Rowling has taken time off from a recent (and inexplicable) venture into laying out wizards’ toilet habits from days of yore to give her readers a glimpse into the thinking behind the writing that has made her one of the world’s best loved and highest paid authors.

Steering clear of what she calls “lists of must do’s”, Rowling points out that she found success as an author “by stumbling off alone in a direction most people thought was a dead end, breaking all the 1990s shibboleths about children’s books in the process. Male protagonists are unfashionable. Boarding schools are anathema. No kids’ book should be longer than 45,000 words.” So instead of advising would-be writers what they have to do, she tells them instead what qualities they can’t do without.

These include the obvious ones, including reading widely, and discipline, as well as resilience and humility. (“The harshest critic is often inside your own head. These days I can usually calm that particular critic down by feeding her a biscuit and giving her a break, although in the early days I sometimes had to take a week off before she’d take a more kindly view of the work in progress.”) A writer must have courage and independence, too. (Which must mean the best writers are all Gryffindors.)

More practically, she also points beginners towards the resources at Writer Beware, describing the website as “fantastic … for anyone who’s trying to decide what might be useful, what’s worth paying for and what should be avoided at all costs”.

The final segment of Rowling’s three-part series On Writing gives a little insight, perhaps, into Pottermore’s ill-advised tweet last week, about how wizards went to the toilet before the advent of plumbing. (Spoiler: wherever they stood, using vanishing spells to get rid of the evidence.) Rowling says she could “have spent literally every hour of every day discussing Potter characters, plot twists and theories with fans over the last 10 years”, but she tries not to give in to the temptation, in order to work on new things. With the spin-off films, sequel play, Pottermore and constant flood of new merchandise, she might be struggling to stick with her own advice.