The Edinburgh-based writer took to social media to describe some of the rude snubs she received from the industry as she began her career, and then turned her attentions, initially anonymously as Galbraith, to crime novels. Writing on Twitter, Rowling revealed one publisher who turned down Harry Potter also send “the rudest rejection” of her book.

She also joked she now has “over a million folders” all made of “costly silks” after a publisher kept the one she sent a manuscript in – much to her disappointment at the time.

In 1996 the first Harry Potter book was turned down by 12 publishers before being picked up by Bloomsbury. The series went on to sell more than 450 million copies.

The Cuckoo’s Calling, which Rowling published under the name Robert Galbraith, sold less than 500 copies in 2013 before she was accidentally unmasked as its author.

Prior to this she also published her first adult fiction novel, The Casual Vacancy, as JK Rowling. It was recently turned into a BBC serial.

In reply to fan Megan who asked: “How many no’s did you get before you finally got published?”

Rowling said: “Loads! First publisher to turn down Harry also sent Robert Galbraith his rudest rejection. They don’t even want me in a beard.”

Another aspiring writer called Kara asked: “Did you ever get nervous emailing agents when you first started out? I always feel nervous.Waiting for a reply is the hard part.”

To which Rowling replied: “The first agent I ever queried sent back a slip saying ‘My list is full. The folder you sent wouldn’t fit in the envelope.’

“I really minded about the folder, because I had almost no money and had to buy another one.”

Fan Jeassamine then questioned: “So how many folders do you have now JK?”

“I now have over a million folders,” Tweeted Rowling. “All made of costly silks, each one hand-gilded by artisans in Paris.”