Well, Richmal Crompton did say in a radio interview that when she started writing these 'Just William' stories, her intention was to write those stories for adults about children.
Listen to the interview :
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The relevant transcript:
> Well I began to write them entirely for adults about children. And they were published in these magazine stories, adult magazines, for adults about children. But they've gradually drifted onto the shelves of junior libraries in libraries and shops. So now I find myself occasionally writing down a bit, but I try not to.