You can't find any legit sources because there are no legit sources. Using Google's search tools to perform a date-limited search on content suggests the original version of this story was published on Uncyclopedia, which is a humour site devoted to parodying Wikipedia that launched in 2005. The page is still there, much modified but very obviously intended to be humorous – to some, I suppose; it includes lines such as "he got a job as the local rapist at age 15". The entry also incorporates a "photograph" of the supposed 16th-century killer, obtained "using witchcraft".

Accessing Uncyclopedia's update history page, we can see that the entry was created in June 2007 by a user called "Jocke Pirat" who appears to be a prolific contributor to the site. It began as a single line of text and has been progressively elaborated ever since.

We can also use Google search tools to suggest no use of the specific terms used in this entry – the name of the supposed killer, Frederic Thomas Lynwood, or the nickname "Drury Lane Dicer" – appears to antedate 2007, and none of these terms appear in any books digitised by the Google Books project. Unfortunately, these precautions have not been taken by every writer who has encountered the story online in some form outside Uncyclopedia, with the result that apparently serious recaps of the tale, stripped of the obviously humorous elements, have appeared in more sober form on sites such as Medium and Londontopia.