[1] Turnbull was appointed an Overseas Development Institute Fellow in 1968 and was posted to work as an economist in the Ministry of Commerce, Industry and Foreign Trade in Lusaka, Zambia.

When Turnbull succeeded to the dual role on 2 September 2002,[3] Prime Minister Tony Blair asked him to focus on the management of the civil service, and to make its reorganisation his priority.

[2] Turnbull became involved in controversy when on 28 February 2004 he wrote a formal letter admonishing ex-minister Clare Short for making media statements alleging that British intelligence had intercepted communications from (among others) Secretary General of the United Nations Kofi Annan.

Short made the confidential letter public, and in turn rebuked Turnbull for allegedly allowing the government decision-making machinery to crumble in the run-up to the 2003 Iraq war.

[11] On 20 March 2007, the day before the 2007 budget was announced, he gave an interview with the Financial Times in which he described Gordon Brown as acting with "Stalinist ruthlessness",[12][13] contrary to the convention that former civil servants do not talk to the media about serving government ministers.