Sir Robert Anderson was born in Dublin, Ireland in 1841. He became a lawyer and married in 1873. In 1876 he became employed by Scotland Yard in Special Branch, investigating the actions of the Fenians (a Victorian group similar to the Irish Republican army or IRA). He was involved in the investigation of the Phoenix Park Murders, in which two British government officials were killed, in 1882. By 1886, Anderson had made an enemy of the Home Secretary and was relieved of all official duties save the handling of Thomas Beach, a spy who had infiltrated the Fenians.
In August of 1888 James Monro became Commissioner of the CID (Criminal Investigation Division) and Anderson was promoted to Assistant Commissioner. Shortly after Anderson's promotion, the first canonical victim, Polly Nichols, was killed.
Anderson's memoirs reveal that he was an early proponent of the idea that the Ripper was "a Polish Jew" and that "he had been safely caged in an Asylum", a theory which most likely refers to Aaron Kosminski.