JK Rowling is not to be contended with when it comes to social network Twitter. The author and public figure is known for being forthright in her replies to trolling tweets. In her latest cutting response she defended six times Wimbledon champion Serena Williams after a Twitter user claimed that she had won the trophy simply because of her masculine figure.

Shortly after the impressive win in Saturday’s women’s final, JK sent a congratulatory tweet, praising Serena as a role model and champion for women.

But one user chose to offer up a critique of Serena’s win, claiming that she had only managed to beat her opponent due to her masculine build.  ‘@jk_rowling @hansmollman ironic then that main reason for her success is that she is built like a man’.

JK didn’t take kindly to the hateful tweet and was quick to respond by tweeting an image of Serena looking stunning in a bold red dress and labeling the Twitter user an ‘idiot’. So far the tweet has been retweeted 82,000 times.