[2] Williams joined the Department of Foreign Affairs and Trade upon leaving university and took postings in Shanghai, Dar es Salaam, Bonn and Tehran.
From 1992 to 1994 he directed in the Trade Negotiation Division and was Director of the Management Strategy and Coordination Unit (1997–1998).
[2] As Director in the Overseas Property Office from 2002, Williams was appointed in late 2003 as the Administrator of the Australian Indian Ocean Territories, which incorporates Christmas Island and the Cocos (Keeling) Islands.
As administrator on Cocos, Williams was responsible for proclaiming the adoption of the official flag of the territory on 6 April 2004.
Serving until 2005, Williams returned to DFAT and was Director of Consular Operations until 2007, and was appointed High Commissioner to Cyprus on 30 April 2008.