First off, let me state that the person behind this script knows very little about the Jack The Ripper killings. I have bad news for people out there, Sir William Gull was NOT Jack The Ripper. I am not saying I know who is, many theories abound, but the 'Queen Victoria sending her personal physician out to kill the prostitutes that gave her son VD' is one of the more laughable.
Secondly, Johnny Depp simply could not emit a convincing British accent. Don't get me wrong, he is a damn good actor, but he was in way over his head with this one.
If you need to see a good Jack The Ripper movie, I would recommend Hitchcocks' "The Lodger"