He was educated in
Gonzaga College, Dublin and graduated from
Balliol College, Oxford with a
Master of Arts (MA) (Greats/Classics). He was elected
President of the Oxford Union in 1974. He entered the Irish diplomatic service in 1977. His father,
Bob McDonagh, and brother,
Philip McDonagh, also served as ambassadors in the service. He is regarded as an expert on
European Union affairs, having spent 23 years of his career either in the corridors of Brussels or in the EU division of the Irish Department of Foreign Affairs. This included periods in the Secretariat of the
European Parliament, periods in the cabinets of two European Commissioners and a period (2005–2009) as the Irish Permanent Representative to the EU. He served as
Ambassador of Ireland to Italy (2013–2017) and retired in 2018. ==Publications==