In the Dictionary of New Zealand Biography Len Richardson described Robert Semple as one of the most colourful leaders of the New Zealand labour movement in the first half of the twentieth century. Semple was a national figure in his time and, although historians had outlined some aspects of his public career, there has been no full-length biography written on him. In New Zealand history his characterisation is dominated by two public personas. Firstly, he is remembered as the radical organiser for the New Zealand Federation of Labour (colloquially known as the Red Feds), during 1910-1913. Semple’s second image is as the flamboyant Minister of Public Works in the first New Zealand Labour government from 1935-49. This thesis is not organised in a chronological structure as may be expected of a biography but is centred on a series of themes which have appeared most prominently and which reflect the patterns most prevalent in Semple’s life. The themes were based on activities which were of perceived value to Semple. Thus, the thematic selection was a complex interaction between an author’s role shaping and forming Semple’s life and perceived real patterns visible in the sources. Chapter one explores Semple as an Australian New Zealander whose relationship with his homeland was a complex one, continually affected by issues such as time, place and political expediency. Chapter two considers Semple in the identity which was arguably the most radical in New Zealand historiography – the Socialist. Several facets of Semple’s socialism will be examined including militant socialism, from which his radical persona was formed, state socialism and practical socialism. To improve the lives of working people was Semple’s aim in life, so the third thematic chapter examines Semple’s role as a union organiser – this was a vehicle through which he pursued this aim. It was from this image that Semple’s public career was founded and then sustained. In the fourth chapter Semple, the Labour politician will be examined. Here his ultimate aim was to improve conditions for all New Zealanders and the several arenas in which Semple pursued this end included party activities, municipal politics and ministerial office. In these two chapters changes in Semple’s political perspectives can be seen as labour concerns became subservient to national concerns when he became part of the Labour government. Chapter five examines Semple as an anti-militarist which was the image where the greatest change in political perspective was evidenced. Semple, the anti-conscriptionist of one world war, drew the marble for the first conscription ballot in the next. These themes are not the only ones in Semple’s life but appear most consistently during his lifetime.