Tony Aust has already produced Modern Treaty Law and Practice (Cambridge University Press, 2000). This was an exercise in the handbook mode which some scholars profess to dislike, and which most of them certainly neglect. In my own case I confess that his handbook is often to hand, because it is a place to start looking at problems in the law of treaties on an everyday basis. It does not claim to be definitive, but it succeeds in its task of introducing and of providing initial guidance in a clear and well-informed way. Take for example the short discussion on provisional application (ibid., pp. 139–41), an issue of great practical significance as to which there is little or nothing in the older treatises. What he says is clear, well illustrated – one is pointed to difficulties and prominent instances (e.g. the Energy Charter Treaty) – and one is told that the case of provisional application which everyone knows – GATT 1947 – is ‘hugely atypical’.

The clear guidance and practical sense of Modern Treaty Law and Practice is here repeated on the broader canvas of general international law, an area of equal significance but much less accessible than the law of treaties. These days everyone including taxi-drivers talks about customary international law, although they probably (and wisely) do not use the term.