Magnussen was a strong defender of the naturalistic style at a time when modernism came to play a still more dominant role on the art scene. He was a member of Charlottenborg's censor committee and a board member both of Dansk Billedhugger Samfund, Kunstforeningen af 18. November and Foreningen for National Kunst, He was an art critic at
København (192026),
Nationaltidende and other newspapers. He was a member of Foreningen til Hovedstadens Forskønnelse in 192842 and served as its president in 1929–34. His writings included his memoirs
Billedhugger-Minder (1933), monographies about
Janus la Cour (1928),
Carl Bloch (1931),
Christian Molsted (1935),
Svend Hammershøi (b. 1936) and
Godfred Christensen (I-II, 1939–41) as well as
I Thorvaldsens Livsanskuelse (1936) about
Bertel Thorvaldsen and
Søren Kierkegaard set udefra (1942). He was editor of
National Kunst (1940) and
Danmarks nationale Malerkunst (1941). ==Personal life==