Abstract The generalised second law of black hole thermodynamics states that the sum of a black hole's entropy and the entropy of all matter outside the black hole cannot decrease with time. Its violation via the process in which a distant observer extracts work by lowering a box arbitrarily close to the event horizon of a black hole has two profound ramifications: (1) the entropy of the universe can be decreased arbitrarily via this process, and (2) it is not appropriate to apply the laws of thermodynamics to systems containing black holes. In this paper, we argue that for the generalised second law to be preserved, entropy must be produced during the lowering process. To demonstrate this, we begin by deriving an equation for the locally measured temperature of the vacuum state of an observer that is a finite distance from a Schwarzschild black hole. Using this locally measured temperature and the Unruh effect, we derive an equation for the force required to hold this observer in a stationary position relative to a Schwarzschild black hole. These equations form a framework for calculating the change in black hole entropy in the case where the lowering process is isentropic and in the case where entropy is produced during the lowering process. In the latter case, two requirements: (1) that the change in black hole entropy is finite, and (2) that the change in common entropy is finite, are used to identify a set of possible functions describing the production of entropy. For this set of functions, we demonstrate that entropy production limits the amount of work the distant observer can extract from the lowering process. We find that this allows for the generalised second law to be preserved, provided a coefficient in this set of functions satisfies a given bound.