Born : 1852
1880 : Gave up studying medicine at St Bartholemew's Hospital and joined the City Police force.
1884 : Made a Detective Constable
1888 : Promoted to Sergeant
1889 : Made a Detective Sergeant
1890 : Promoted to Detective Inspector
1905 : Retired
1924 : Died
Henry Smith (Commissoner City Police 1890-1901) wrote "A better or more intelligent officer than Robert Sagar I never had under my command."
"Reynolds News" (15 September 1946) printed an extract from Sagar's unpublished, and now untraced, memoirs. Sagar wrote that "We had good reason to suspect a man who worked in Butcher's Row, Aldgate. We watched him carefully. There was no doubt that this man was insane, and after a time his friends thought it advisable to have him removed to a private asylum. After he was removed there were no more Ripper atrocities."
Although there are some differences this could possibly be referring to Swanson's suspect Kosminski. If this is the case it is significant because it suggests that the City Police, to which Sagar belonged, and the Metropolitan Police, to which Swanson belonged, were following similar lines of inquiry. While Sagar was probably aware of Robert Anderson's statements about the ripper being "caged in an asylum" etc he would not have known about the Swanson Marginalia which did not come to light until some 40 years after the above extract was published.
As somebody who had studied medicine, even if only briefly, and was involved in investigating the murders it would have been interesting to have known Sagar's opinions on the amount of skill displayed by the killer.
Begg, Fido, and Skinner. The Jack the Ripper A-Z.