Arthur Conan Doyle was the first person to advance the brilliant theory that Jack the Ripper committed his murders whilst in drag.

In 1888, Conan Doyle told police officials that he thought the murderer could be disguised as a midwife.

Thus, 'she’ could be seen with bloody clothes without attracting undue suspicion - and would be more easily trusted by female victims.

Later, 'Ripperologist’ William Stewart went further, proposing that the murderer was actually a woman – and even went as far as naming her.

Dubbing her 'Jill the Ripper’, Stewart suggested it was Mary Pearcey (pictured, looking both Victorian and evil), who in October 1890, killed her lover’s wife and child.

E. J. Wagner, in The Science of Sherlock Holmes, offers the further ludicrous suggestion that it was Constance Kent (of The Suspicions of Mr Whicher fame), who had served 20 years for the murder of her younger brother at the age of sixteen.

Though these theories are fairly unlikely, DNA evidence taken from the 'Ripper letters’ (sent to the police in 1888, supposedly by the murderer) suggest the envelopes may have been sealed by a woman…