Author JK Rowling, 49, responded by branding the troll an 'idiot' and posting an image of Serena looking

JK Rowling already has form when it comes to putting people in their place on Twitter. She famously once advised someone they might want to buy a 'penis enlarger'.

So when a troll replied to a congratulatory tweet from Rowling to Serena Williams following her sixth Wimbledon win yesterday with a body-shaming comment, the Harry Potter writer didn't hold back.

The troll, who had attributed William's tennis success to her being 'built like a man', was quickly slammed down by 49-year-old Rowling, who branded them an 'idiot'.

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Harry Potter author, JK Rowling, 49, defended Serena Williams after a Twitter troll directed body-shaming comments at the tennis star

Serena Williams, 33, soared to victory, clinching her sixth Wimbledon win on Saturday

Williams, 33, soared to victory on Saturday, beating Spain's Garbine Muguruza, 21, in the women's tennis final, and completing her 'Serena Slam' as holder of all four major tennis titles.

As messages of congratulations poured forth for the American world number 1, Rowling, who had tweeted excitable updates to her 4.92 million followers throughout the match, also took to Twitter to express her delight at the win.

The famous Harry Potter author gushed: '#SerenaSlam! I love her. What an athlete, what a role model, what a woman!'

However, one Twitter user took issue with the latter part of Rowling's tweet, responding: '@jk_rowling @hansmollman ironic then that main reason for her success is that she is built like a man'

'#SerenaSlam! I love her. What an athlete, what a role model, what a woman!': JK Rowling gushed about the tennis star following her Saturday victory

The body-shaming tweet, sent by Rob, @diegtristan8, was not taken to kindly by Rowling, who replied in cutting fashion.

The author posted two images of 33-year-old Williams pictured posing for fans in a red figure-hugging knee-length dress.

In the images, the tennis star looks resplendent in the scarlet ensemble, paired with studded Louboutin platforms - which serves to show off her enviable figure.

Rowling proves her point and deflects the Twitter users comments along with the caption: '"she is built like a man". Yeah, my husband looks just like this in a dress. You're an idiot.'

'"she is built like a man". Yeah, my husband looks just like this in a dress. You're an idiot.' The author reacted to the body-shaming comment by proving her point with an image of Serena looking sensational

The 49-year-old author's cutting and effective response has since been retweeted over 650,000 times and favourited 84,491 times.

And this isn't the first time that the Rowling has taken to social media in order to express her unfiltered opinions.

Back in May, the novelist, who is married to 44-year-old anaesthetist Neil Murray, humorously took to Twitter to share her shock over newly-released images of actor Matthew Lewis, 25, who played the timid character of Neville Longbottom in the Harry Potter film franchise.

The actor has enjoyed a nerdy-to-hunky transformation which saw him take to the cover of Attitude magazine to debut his new look - in revealing white boxers, no less.

Author JK Rowling is a huge fan of world no. 1 Serena Williams, who soared to victory at Wimbledon on Saturday

Rowling and Lewis' embarrassed Twitter exchange saw her jokingly reprimand him, saying ‘now go put some clothes on’.

Earlier in May, during a discussion on the British elections, the author was also victim of hateful Twitter abuse, which saw her labelled 'JK b****face'.