Some would say investment arbitration has reached its half-life. Emerging from, or in reaction against, earlier inter-state forms – diplomatic protection, FCN treaties, etc – it has a kind of ‘boom-and-bust’ feel to it. Ad hoc tribunals have produced an erratic pattern of decisions, with reasoning often impressionistic and displaying a certain disregard for state regulatory prerogatives. This is leading in turn to a reaction by some host states. Meantime there is much that is uncertain and unpredictable.

Zachary Douglas is unsparing in his criticism of particular decisions. But he does not accept either the rose-tinted view that the international investment tribunal is a new form of merchants' court, dispensing a relatively unconstrained justice – or the sceptic's alternative view that there is no point in the quest for explanations, and thereby for greater certainty. Rather he seeks to provide guidance, to say the law, even in Diceyan propositional form.

One characteristic of the field of investment arbitration is the overlapping and interaction of laws and legal systems. In analysing this phenomenon, Douglas displays fluency not only in public international law but also in private international law, adding greatly to the strength of his analysis – and to the collected wisdom of Dicey!

But there is much more. Douglas brings to his work a solid understanding of the functions – and sometimes dysfunctions – of international arbitration, generated by his practical and professional experience.