Of course, Rowling created the expansive, magical world of Hogwarts Castle with its rolling grounds and fabulous feasts when she was a single mother on benefits. She is not short of a bob or two now, I understand, and with the ability to go wherever she likes in the world, her imagination seems to have become drawn to the insalubrious. She is, perhaps, ready now to draw on her own memories of poverty to evoke the circumscribed life of the dirt-poor Strike, reduced to sleeping on the floor of his tiny, smelly office, in a dingy part of Soho that is brought to life with as much conviction as Diagon Alley.

Those who know about Rowling’s battles with the press over her privacy will not be surprised that the Rita Skeeters of the muggle world come in for sharp comment in the Strike books. Perhaps the emotional core of the series is Strike’s difficult relationship with his famous rock star father; and the reason this storyline has such power may have much to do with Rowling’s fears, as revealed in her testimony to the Leveson Inquiry, about the damaging effects her fame may have had on her own children.

But if Rowling had had her way, none of us would be trying to pick out the autobiographical elements in her crime fiction, or make comparisons with the Potter saga. I asked David Shelley, Rowling’s editor at the publisher Little, Brown, why she had taken a pseudonym.