This paper will examine the sustainability of directors’ duties from two perspectives, namely that the duties are stable in their own right and that they cover enough ground for them to help achieve sustainable goals. First, we will examine how directors’ duties to act in a company’s best interest operate well when shareholder interests are aligned. These duties, when breached, can be ratified by shareholders given the traditional understanding that they are the company. This may, in turn, have been associated with the growing acceptance of shareholder primacy over the past 40 years, seen most recently in the UK Supreme Court decision in BTI v Sequana (2022). The Supreme Court, however, also discussed the limitations of shareholder ratification, and its interaction with the rules protecting creditors, particularly as regards capital maintenance. Those rules have, however, been weakened, and private law has had to step in to address the abuse those rules were aimed at. Where the substantive content of directors’ duties is concerned, the focus everywhere is on how to make directors take account of external constraints such as environmental, social and governance (ESG) concerns and corporate purposes that may contradict enhancing shareholder value (as well as existing shareholder protection) as an established paradigm of company law. We will also analyse the difficulties in accommodating the interests of other internal constituents, like creditors (some of whom may have been externalised). This paper will build on earlier suggestions that the proper purpose rule has a part to play in balancing the interests of corporate constituents both inter and intra se and even in considering the position of future shareholders. The test of what is in the best interest of the company may not provide enough balance in this regard, as seen perhaps from the recent failed derivative action sought by some shareholders of Shell against its directors, and directors should take account of the interest of the reasonable shareholder in capturing the gist of what ESG should aim at.