The doctrine of vicarious liability has its roots in the early common law, with its core elements coming to be determined in the Victorian era. The ambit of the doctrine thereafter remained fairly settled until around the start of the present century, but since then its reach has been expanding markedly. This article will seek to explain exactly how the law has been expanding, which requires an examination both of the types of relationships where vicarious liability can apply and, assuming the requisite relationship exists, the nature of the link between the relationship and the wrongdoing in question. A further question concerns the circumstances in which a non-delegable duty may be imposed. Here, exceptionally, the duty is not simply to take care but, more onerously, extends to care being taken by another person to whom the task of performing the defendant’s duty has been delegated. How vicarious liability and the concept of the non-delegable duty relate to each other, and whether or when they can overlap, will be examined and explained. The ultimate aim of this article is to consider why the law has been moving in these various ways, to identify the relevant policy concerns and to reach a conclusion on where it ought to stop.