He also holds a B.Litt from Australian National University and a graduate diploma in applied finance from the Securities Institute of Australia (today FINSIA).

Between March and June 2000, he was the Chief Negotiator of the Peace Monitoring Group on Bougainville, before returning to Phnom Penh as chargé d'affaires between July and October that year.

[6] After his time at the Bangkok embassy, Grigson became Deputy Secretary of the DFAT, and he later became Australia's Special Representative to Pakistan and Afghanistan.

[2] Grigson was recalled on 29 April 2015 following heightened tensions between Indonesia and Australia caused by the execution of Australian drug couriers Andrew Chan and Myuran Sukumaran.

[8] Grigson started working as the Deputy Secretary of Infrastructure, Transport Security and Customs of the Department of Home Affairs on 19 February 2018.