Jack the Ripper may have committed his first murder 25 years earlier than previously thought, it has been claimed.

Jack the Ripper may have committed his first murder 25 years earlier than previously thought, it has been claimed.

An investigation by retired homicide detective Trevor Marriott has also suggested that the notorious 19th-century serial killer did not, in fact, remove internal organs from two of his victims.

Mr Marriott, who will present his findings in a lecture at London's Docklands Museum today, has uncovered case files on the murder of a London prostitute in 1863 which he believes fits the Ripper's "modus operandi" - a quarter of a century before the first official Ripper case.

A 28-year-old prostitute named Emma Jackson was found dead at a brothel in St Giles, central London, in April 1863.

She had five wounds to the throat and had not been robbed. The case was never solved.

Mr Marriott also uncovered a second case he believes may have been committed by the Ripper. Nine years after the Jackson murder, on Christmas Day 1872, Harriet Buswell was found with her throat slit at her lodgings in nearby Great Coram Street, after returning home the previous evening with a male guest, who witnesses reported to be German.

This case also remains unsolved but Mr Marriott's previous book on Jack the Ripper claimed that the murderer was a German merchant seaman named Carl Feigenbaum.

In his new book, The Evil Within, Mr Marriott claims it would have been impossible for the murderer to extract organs from his victims, including his second "official" victim Annie Chapman and Catherine Eddowes, his fourth, with a degree of medical precision.

Mr Marriott said: "The organs were not removed by the killer at the crime scenes, but by person or persons unknown for medical research at some point between the bodies being removed from the crime scenes and the post mortems taking place some 12 hours later."