The Case in the Documents?

[igenlode]

This news story from the 1920s must surely have been in the mind of Dorothy L. Sayers when she was creating the character of Margaret Harrison in her novel The Documents in the Case... those cited letters (I was buoyed up with the hope of the 'light bulb' and I used a lot — big pieces too — not powdered — and it had no effect — I quite expected to be able to send you that cable — but no — nothing has happened from it) could almost be direct quotes. Which is ironic, as successive critics have complained that Margaret's self-dramatising, emotional yet commonplace letters are the weakest and least plausible part of the book!

https://www.bbc.co.uk/news/uk-england-london-63561245