Christian Michelsen, a shipping magnate and statesman, and Prime Minister of Norway from 1905 to 1907, played a central role in the peaceful separation of Norway from Sweden on 7 June 1905. A national referendum confirmed the people's preference for a monarchy over a republic. However, no Norwegian could legitimately claim the throne, since none of Norway's noble families could claim descent from medieval royalty. In European tradition, royal or "blue" blood is a precondition for laying claim to the throne.