The focus of this paper is on the peculiarities of Lohne 's "outsider approach" to the historiography of mathematics and physics. The main thesis is that the circumstances of Lohne 's outsider position both narrowed down and sharpened the focus of his research, but that he succeeded because he joined the then rising tide of archival based and content oriented internalist research in the history of physics and mathematics and because he was supported by scholars such as D.T. Whiteside and J.E. Hofmann , whose connections to the international community were better than his own. The main conclusions are based on Lohne 's Nachlass in Oslo and on some other archival sources. In addition Lohne 's publications are used, which were mostly in English and German, and partly in Norwegian. We do not, however, discuss Lohne 's contributions to the historiography of mathematics and physics in any detail, because they are published and accessible. We merely sum up two outstanding results of Lohne 's research on Thomas Harriot (1560–1621), concerning the discovery of the sine law of light refraction and the calculation of the Mercator map, in order to stress the quality of his work and his critical mind and to give some idea about his historical method. Concluding the paper we reflect once again, on the basis of our biographical evidence in the case of Lohne , and with some emphasis on Scandinavia, on the relative notions of the "outsider" and the "main stream" within the process of professionalization of the historiography of mathematics and sciences in the second half of the 20th century.