You should get your hands on Sayers' nonfiction writing in any form. She's just as tart & full of vinegar as you'd expect, and deliciously direct, especially when it comes to fending off the opinions of others in regards to her work—and the fierce autonomy of her fictional characters as specific, separate entities who will obey neither your expectations nor, in many ways, her own.
From The Mind of the Maker:
Well-meaning readers who try to identify the writer with his characters or to excavate the author's personality and opinions from his books are frequently astonished by the ferocious rudeness with which the author himself salutes these efforts at reabsorbing his work into himself. They are an assault upon the independence of his creatures which he very properly resents. Painful misunderstandings of this kind may rive the foundations of social intercourse, and produce explosions which seem quite out of proportion to their apparent causes ....
"I am sure Lord Peter will end up as a convinced Christian."
"From what I know of him, nothing is more unlikely."
"But as a Christian yourself, you must want him to be one."
"He would be horribly embarrassed by any such suggestion."
"But he's far too intelligent and far too nice, not to be a Christian."
"My dear lady, Peter is not the Ideal Man; he is an eighteenth-century Whig gentleman, born a little out of his time, and doubtful whether any claim to possess a soul is not a rather vulgar piece of presumption."
"I am disappointed."
"I'm afraid I can't help that."
(No; you shall not impose either your will or mine upon any creature. He is what he is, I will work no irrelevant miracles upon him, either for propaganda, or to curry favour, or to establish the consistency of my own principles. He exists in his own right and not to please you. Hands off."