A forensic linguist from The University of Manchester who analysed letters supposedly signed by Jack the Ripper has concluded that two of the most famous examples were written by the same person.
The Whitechapel murders that terrorised London in 1888 are still remembered thanks to the legend of Jack the Ripper, who was never caught.
In addition to the gruesomeness of the murders, Jack the Ripper’s name and persona were popularised by more than 200 letters which were received following the murders. These letters are essentially what made him famous, and it has often been suggested that they were written by journalists to sell more newspapers.
http://www.manchester.ac.uk/discover/news/jack-the-ripper-letter-mystery/
https://academic.oup.com/dsh/advance-article-abstract/doi/10.1093/llc/fqx065/4824843