About ten seconds of search at IMDB, or, having actually seen the movie, pretty much calls into question the quality of this writer's research skills.
Depp was NOT Jack; he played the good guy, Inspector Frederick Abberline.
*** MILD SPOILER ALERT ***
The interesting plot twist in the film centers around the actual identity of Jack, and the motivation for killing prostitutes, one of whom was a Roman Catholic. It's a theory developed in several of the other Ripper "histories," and it's actually not too bad.
In addition, the following passage calls into question the quality of the writer's writing skills:
"Trevor Marriott spent 11 years pouring over Scotland Yard files..."
Pouring what over the files? Water? Beer? If the writer means "looking intently through the files," the correct verb is poring - no "u"!
Sorry to play grammar police, but this is supposed to be someone who writes for a living - not just one of us posting a comment! Anyone who writes for a living should know that those are two different verbs. /Rant off!