In c. 1911, he became a King's Counsel, and on 28 April 1914, he was appointed to the Supreme Court of Western Australia bench.
[3] On 29 September 1931, he became the Chief Justice of Western Australia, following the death of Sir Robert McMillan in April 1931.
[4][5] On 29 June 1932, he became Lieutenant-Governor,[1][6] which he served as until 10 July 1933, when he resigned due to Thomas Draper, senior puisne judge.
[6] Within the University of Western Australia (UWA), Northmore was pro-chancellor from 1929 to 1930, member of the senate from 1930 to 1936, and chairman of its finance committee.
[1] Northmore married Emily Agnes Ventris (née Culmer), on 6 March 1941 in a private Anglican chapel.