According to an Express UK article, detective Trevor Marriot asserts that there never was any such person as Jack The Ripper. Marriot postulates that a drunken journalist faked the earliest letters and that the rest was filled in with hoaxes, etc.
But as the Anomalist points out, there are a number of holes in this theory:
"This is a bold claim and it's not the first to be made about the identity of the vicious killer who terrorized Victorian London and left behind a trail of five bodies and most likely a lot more that were never accounted for. This new theory, dreamed up by detective Tervor Marriot, proposes that Jack the Ripper never existed at all but was instead dreamed up by a "drunken journalist" who faked the initial letter to the editor. Marriot claims there was a string of unsolved murders in the area that may have been committed by the same person but that the details of the prostitute murders were entirely fabricated. However, this theory has some awfully big holes in it that Marriot seems to ignore entirely, including his belief that Jack wore the clothing of a wealthy gentleman and would never have survived being on the dangerous streets of London at night. His proof? The countless images of Jack the Ripper that pervade the media showing him dressed in a top hat and cape. Nothing in any eyewitness account mentions a man in a cape and in fact, much evidence points to the seemingly obvious fact that a devious, intelligent murderer like the Ripper would think to disguise himself in different clothes! We don't put much stock into this new theory but we also aren't convinced by many of the other theories either, from Patricia Cornewell's ridiculous claims about artist Walter Sickert to the belief that The Ripper was a woman. The truth is that no one will ever solve the mystery behind Jack the Ripper's identity and he will live on in legend, which is probably exactly what he wanted."
Although, I have to say I read Cornwell's treatise on Sickert as the Ripper and I found it compelling. To call it ridiculous is to say that it had no merit whatsoever. Was it airtight? Hardly. But she made some rather intriguing correlations and deductions. Plus, she did what few others have done well: looked at the forensic science.
I agree, though, that we are unlikely to ever know who the Ripper was. Each year the case grows colder and the layers of time build up like a patina to obscure the truth. But a breakthrough may await us still and I think that's part of why the Ripper legends keeps us so fascinated.