New analysis of two letters, supposedly written by the infamous serial killer Jack the Ripper, suggests that they may have been penned by journalists hoping to improve newspaper sales.

The 'Dear Boss' letter - in which the name 'Jack the Ripper' was first used - and the 'Saucy Jacky' postcard were both received by the Central News Agency in 1888. It has long been suggested that both letters were hoaxes.

Speculation about the true identity of the killer - who murdered at least five victims in London's East End in 1888 - is rife to this day. It remains one of the most notorious cases in British criminal history.

Computer analysis by the University of Manchester's forensic linguist Dr Andrea Nini now suggests that both were from the same author.

Nini conducted an analysis of 209 letters sent to police or newspapers, supposedly by the Ripper, and found clear similarities between them.

Importantly, the same linguistic characteristics were found in a third message - the Moab and Midian letter - forwarded to Scotland Yard by journalist Thomas Bulling, leading the police to believe he wrote it. This letter is considered one of the most likely hoaxes.

Similarities between the three include the use of the saying "to keep back" instead of the more popular Victorian phrase of "to withhold" and the use of the word "work" to mean killing, the BBC reported. Both letters also include "ha ha" to depict laughter.

The Moab and Midian letter spoke of a triple murder and promised to deliver "a bit of face". All of the Ripper's confirmed killings were single murders.

"These results constitute new forensic evidence in the Jack the Ripper case after more than 100 years, even though they do not reveal information about the identity of the killer", Dr Nini said.

"People in the past had already expressed this tentative conclusion, on the basis of similarity of handwriting, but this had not been established with certainty."

Nini suggested it is likely the letters were "works of fiction skillfully created to generate shock and keep business alive".

The 'From Hell' letter remains one of the most chilling of all 209 letters received, delivered in a box containing half of a kidney preserved in ethanol. A doctor at the London Hospital determined the grisly gift to indeed be a human kidney. One of the victims - Catherine Eddowes - had her left kidney removed after she was killed.

A victim of Jack the Ripper is discovered in Whitechapel
A victim of Jack the Ripper is discovered in Whitechapel Wikicommons