JK Rowling reveals she had one of her greatest Harry Potter ideas... on an aeroplane sick bag

You can never be sure where inspiration will strike. For JK Rowling, the tale of her boy wizard Harry Potter "fell" into her head on a train to London.

But the best-selling author has revealed that was far from the strangest place for her to be seized with an idea for her books...

Rowling was on Twitter responding to a thread about writers in which author Ruth Ware observed that, unlike others in her profession, she did not carry a notebook with her everywhere.

Rowling's comments prompted another tweeter to share their experience of writing notes on a napkin – which prompted the Harry Potter author to post this gem of an anecdote:

The Hogwarts houses – Gryffindor, Ravenclaw, Hufflepuff and Slytherin – are now synonymous with Rowling's Harry Potter universe, with fans the world over identifying as one of the four.

So, it just goes to show. Wherever you may be – the toilet, your desk, flying thousands of miles in the air with a sick bag in hand – you can never be too prepared for that multi-million-selling, genre-defining, franchise-inspiring idea.