Harry Potter and the Cursed Child (Little, Brown) has snatched the Official Top 50 number one for a fourth week, according to Nielsen BookScan’s Total Consumer Market. J K Rowling, Jack Thorne and John Tiffany’s playscript sold 52,719 copies for £652,220, making it the longest-running children’s number one since Judith Kerr’s Mog’s Christmas Calamity (HarperCollins Children's) in November 2015.

This is the first time a Little, Brown title has held the number one for more than three weeks on the trot—beating Rowling’s own The Casual Vacancy, Stephenie Meyer’s Twilight spin-off The Short Sec...