In Part I of this study we undertook a historical overview of IIL and its institutions and examined the core substantive and procedural rules (Chapter 1), mapped tensions (Chapter 2) and normatively conceptualised the reform challenges (Chapter 3). The complexity of this field of international law is magnified by its internal fragmentation – the large number of different legal instruments and their mixed private–public nature. The manner in which the field operates autonomously from other areas of international law supports the wider phenomenon of fragmentation in international law. Finally, the high financial stakes involved in investment have led to further politicisation of this already politicised field of international law.