[2][3] After school, Sainsbury worked as a junior clerk at the Oriental Bank Corporation.

[2] Sainsbury joined Victoria Police on 17 May 1878, he was assigned registered number 2944 and was appointed to Colac as a mounted constable.

[7] Taking command of the force for the duration of World War I, Sainsbury had to oversee a wide range of extra duties undertaken by Victoria Police, including alien registrations, internments and the investigation and arrest of military deserters.

Sainsbury had initially blocked attempts to form the association believing it to be against the principles of the semi-military nature of the police force.

Sainsbury died on 27 February 1920 at his home in Vine Street, Moonee Ponds.