Hagerup was born at Kristiansand in Vest-Agder, Norway. He was the son of Bishop Eiler (Kongel) Hagerup (b. 1718) and Edvardine Magdalene Margarethe Christie (b. 1755). In 1801, he studied at the University of Copenhagen with Wilhelm Frimann Koren Christie. Both became King's representative (Stiftsamtmann) of a county in Norway. During the formation of the Constitution of Norway signed at the Constitutional Assembly at Eidsvoll in 1814, Christie was secretary to the delegates led by Christian Magnus Falsen and Hagerup was advisor to the Danish Prince Christian Fredrik who was present.
He was a member of the first Norwegian Parliament (Storting). In 1814, he was asked to accept the post of Minister, which would have required him to live in Stockholm, so he abstained. At that time, he worked as an Assessor.
Hagerup was later appointed County Governor of Nordre Bergenhus amt (1822-31), (now Sogn og Fjordane). Seated in Bergen, as Nordre Bergenhus was administrated from outside its territory, Hagerup was elected to the Norwegian Parliament from that city for the year 1824. In 1827 he was elected to the Norwegian Parliament for a third time. From 1834 to 1852 he served as County Governor of Søndre Bergenhus amt (now Hordaland).
He was married to Ingeborg Janson (1786–1849), daughter of estate owner, merchant and court agent, Herman Didrik Jansen. His father-in-law saw in Hagerup the most likely custodian of his vast fortune and financed the transport of representatives from Bergen to Eidsvoll in 1814. Hagerup died an extremely wealthy man. Eight of nine children lived to maturity. He was the grandfather of both the composer Edvard Hagerup Grieg (b. 1843) and his wife Nina Hagerup (b. 1845).
Christian Magnus Falsen
| County Governor of Sogn og Fjordane
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