A hundred years ago Fletcher Moulton LJ said of fiduciary duties that ‘[t]here is no class of case in which one ought more carefully to bear in mind the facts of the case’. In the last century nothing has changed to alter the force of this dictum. However, the development of fiduciary duties in England has shown why they are so dependent upon the facts of the case. This is because of their nature as terms which are expressed or implied into voluntary undertakings. The constraints of space in this chapter preclude an explanation of this thesis. I have given that explanation, from a doctrinal perspective, in a longer article elsewhere. The same conclusion, from a contextual ‘contractarian’ approach, is also reached in Tony Duggan's chapter in this volume.

This chapter takes that premiss – that fiduciary duties are voluntary undertakings – as its starting point and shows how such an analysis helps to understand and provide answers to four contemporary puzzles in the law concerning fiduciary obligations. The four puzzles are as follows:

1. (1) Which fiduciary duties can be excluded by agreement?

2. (2) When do fiduciary obligations come to an end?

3. (3) What is the proper law to be applied to fiduciary duties where they arise in a cross-border context?

4. (4) What is the level of fault required before a person can be liable for inducing or assisting in a breach of fiduciary duty?