If there’s one author who knows how to write a best-seller, it’s JK Rowling.

After being rejected by 12 different publishers, Rowling went on to sell 450 million books (and counting) worldwide of her much-loved Harry Potter saga.

Which is why, when some of her 14 million followers on Twitter started to ask her about Lethal White (the upcoming fourth novel in her Cormoran Strike series), it led to an impromptu Q&A about her writing process.

“I plan a lot. This particular novel’s plan comprises a vast, complicated, colour-coded table showing all the suspects, with blue ink for clues and red ink for red herrings,” Rowling wrote, revealing that she uses a colour-coded system.

JK Rowling takes to Twitter to reveal her complex writing process to fans