In 1884, Monro resigned from the Indian Civil Service and returned to Britain, being appointed the first Assistant Commissioner (Crime) in London.

He forged a close alliance with Robert Anderson, the Home Office adviser who controlled the spies infiltrating the Fenians.

Their greatest achievement was in 1887, when they foiled an attempted bombing of Westminster Abbey during Queen Victoria's Golden Jubilee celebrations.

Monro politicked behind the scenes to assert his primacy over the Home Office in the secret world of spying against the Fenians.

Eventually, he was successful and Special Branch, under his control, became the sole force in charge of covert security in the United Kingdom.

Warren also tried to assert his authority over CID, which his predecessor, Sir Edmund Henderson, had left almost entirely in Monro's hands.

Anderson and his senior CID officers continued to consult with him behind Warren's back, particularly during the Jack the Ripper case, with Matthews's complete connivance.

Worn out by constant criticism, Warren resigned in November 1888, and Matthews appointed Monro to replace him as Commissioner.

Monro wanted to replace him with Chief Constable Charles Howard, but the Home Office preferred Evelyn Ruggles-Brise, one of its own high-flyers.

[1] Monro returned to India in 1890 as a missionary, founding and running Ranaghat Christian Medical Mission in the far north of the country.