Sometimes, it's heard to read sarcasm on Twitter. This is not one of those times.

On Friday, JK Rowling wrote: "Twitter really is an amazing resource for a writer," alongside an image of President Trump's recent tweets.

"These screen caps will be a useful reference should I need to create a character of quiet strength, facing his tribulations calmly, fortified by his clear conscience," she said.

Obviously, she was joking.

The five tweets from Trump she was talking about were all sent within a one-hour window about "Leakin' Lyin' James Comey," "Crooked Hillary," and claims of a "Witch Hunt" and DNC corruption.

Ms Rowling's followers replied to her post calling her "the best at snark," and saying Trump "Would give (cruel 'Harry Potter' professor Dolores Umbridge) a run for her money." One fan wrote, "best of it is, if you'd written a character like that, everyone would roll their eyes and say it was a bit of a stretch."

The author has long been a critic of the American president, often without any subtlety. In July, she replied to Trump's now-deleted tweet about having written "many best selling books" and defending his grammatically-incorrect capitalization rules, with lines of "hahahahahahaha" over multiple tweets. Finally, she wrote, "Seriously, @realDonaldTrump is the Gratest Writer on earth."

That too, was sarcasm.