After the end of the First World War, Sellheim became Quartermaster general in 1920 but resigned in 1927 to become Administrator of Norfolk Island, where he died on heart failure in 1928.

[1] After attending courses in the United Kingdom, Sellheim served in the Second Boer War as an officer attached to British units and the chief of staff of Harry Chauvel's Mounted Infantry, taking part in the Battle of Belmont and the Battle of Modder River.

For his services during the war, Sellheim was appointed a Companion of the Order of the Bath[5] and also Mentioned in Despatches.

[1] Sellheim served as the head of the administrative staff in the 1st Division of the Australian Imperial Force.

Sellheim was replaced by Robert Anderson in August and was sent back to Australia to become the Adjutant General again.