Military career

MacWilliam underwent officer training at the Royal Military Academy Sandhurst.^[3] On 20 December 1968, he was commissioned into the Queen's Regiment, British Army, as a second lieutenant.^[3] He was promoted to lieutenant on 20 June 1970,^[4] and to captain on 20 December 1974.^[5]

Having attended the Staff College, Camberley, he was promoted to major on 30 September 1981.^[6] He retired from the British Army on 21 August 1984.^[7] He had seen active service in Northern Ireland during The Troubles,^[2] and in Oman.^[8]

Ecclesiastical career

Having left the British Army, MacWilliam joined the Missionaries of Africa, a Roman Catholic society of apostolic life, who are also known as the White Fathers.^[1] From 1984 to 1986, he studied philosophy at Society's Missionary Institute in London.^[1] He spent 1986 and 1987 in Fribourg, Switzerland, and then spent two years training in the Maghreb.^[1] From 1989 to 1992, he studied theology in London.^[1]

In December 1991, MacWilliam made his vows thereby becoming a professed member of the Missionaries of Africa (M. Afr.).^[9] He was ordained as a deacon in December 1991 and as a priest on 4 July 1992.^[1] He then continued his studies, studying Islam at the Pontifical Institute of Arab and Islamic Studies in Rome between 1992 and 1995.^[1][2]

In 1994, four members of the White Father mission in Tizi Ouzou, Algeria, were murdered in their home.^[2] In 1995, MacWilliam volunteered to go to Algeria to re-open the mission in Tizi Ouzou.^[2] He served in Algeria between 1995 and 2008, during which violence against Christians increased and the Civil War was fought.^[1][2] He then worked in Tunisia.^[1] He has served as Superior Provincial for North Africa (covering Algeria and Tunisia) since 2015.^[1][10]