Donald Hawley joined the Sudan Political Service in 1941, spending the first three years on military service with the Sudan Defence Force. He was recalled to the Political Service in 1944 and served as Assistant District Commissioner in Blue Nile and Kassala Provinces. He joined the Sudan Judiciary in 1947 and resigned as Chief Registrar just prior to Sudanese independence in 1955. The following year he was appointed to HM Foreign Service, serving as Political Agent, Trucial States from 1958, Head of Chancery, British Embassy, Cairo from 1962 and Counsellor and Head of Chancery, Lagos from 1965. After a year as a visiting Fellow at Durham University in 1967, he was appointed Counsellor (Commercial) in Baghdad in 1968 and HM Consul-General, Muscat in 1971. From 1971 to 1975 he was Ambassador to Oman and from 1975 to 1977 served as Assistant Under Secretary of State, FCO, during which time he led a mission to Uganda and visited India, Pakistan and Bangladesh to report on immigration. He retired from the FCO in 1981 after four years as British High Commissioner in Malaysia. He was awarded an MBE in 1955, and appointed CMG (1970) and KCMG (1978).
After retirement from H.M. Diplomatic Service, Sir Donald took up a number of directorships and consultancies, notably with the Ewbank Preece Group, the Hongkong and Shanghai Banking Corporation and the Centre for British Teachers. He served on the Council of the University of Reading from 1981 to 1994, latterly as President and was involved with the University of Durham (where he was a Visiting Fellow in the Department of Geography in 1967) through support for the Sudan Archive and membership of the Sir William Luce Memorial Fund committee. He was awarded an Honorary DLitt by the University of Reading in 1994 and an Honorary DCL by the University of Durham in 1997. He continued to travel widely, particularly in the Middle and Far East, and maintained his interest in those countries where he had served by membership of such bodies as the Sudan Government British Pensioners' Association, the Sudan Defence Force Dinner Club, the Anglo-Omani Society and the British Malaysian Society. Sir Donald died on 31 January 2008.
His publications include Handbook for Registrars of Marriage and Ministers of Religion (Khartoum, 1963), Courtesies in the Trucial States (1965), The Trucial States (1971), Oman and its renaissance (1977) and Sandtracks in the Sudan (Norwich, 1995).