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After a fan asked: "will the Cursed Child make me cry?" Jo responded jokily, writing: "If it doesn't, we'll be checking your vital signs."
Another fan followed up her response, asking: "why are you like this," to which the author responded: "I'm a writer. If you're not feeling, I'm not doing it right."
The Harry Potter author teased fans about the play on Twitter
The play, which is coming to West End this summer and will be staged in two parts, is a sequel following from The Deathly Hallows epilogue and will focus on both the once boy wizard Harry Potter as an adult and his son, Albus Severus, during his first year at Hogwarts.
The official synopsis for the play reads: "It was always difficult being Harry Potter and it isn’t much easier now that he is an overworked employee of the Ministry of Magic, a husband and father of three school-age children.
"While Harry grapples with a past that refuses to stay where it belongs, his youngest son Albus must struggle with the weight of a family legacy he never wanted. As past and present fuse ominously, both father and son learn the uncomfortable truth: sometimes, darkness comes from unexpected places."
The show's Twitter account has been sharing insights into the rehearsals
Jo has previously opened up about how much she was looking forward to collaborating on the production. She said: "The story only exists because the right group of people came together with a brilliant idea about how to present Harry Potter on stage. I'm confident that when audiences see Harry Potter and the Cursed Child they will understand why we chose to tell this story in this way."
.@jk_rowling gives fans a sneak peek inside the #HarryPotterPlay #CursedChild #RehearsalRoomhttps://t.co/bkOFmHb3ew
— Harry Potter Play (@HPPlayLDN) April 22, 2016