He qualified as a solicitor at 19 and as a barrister at 20,[1] and joined his father's Christchurch law firm, Raymond, Stringer, Hamilton and Donnelly.

[2] He served as a sergeant with the New Zealand Expeditionary Force in France in World War I.

[2] He managed the New Zealand cricket team in England in 1931, and played in one of the non-first-class matches at the end of the tour.

Donnelly was appointed Crown Solicitor for Christchurch in 1921, and became chairman of the Bank of New Zealand in April 1937.

[5] He was appointed a Companion of the Order of St Michael and St George, for public services, in the 1939 New Year Honours,[6] and a Knight Commander of the Order of the British Empire in the 1949 New Year Honours.