This paper presents a case study of an Osterberg-cell test of a pile located at the Isle of Dogs in London, which was heavily instrumented with distributed optical-fibre sensors, strain gauges, displacement transducers and extensometers. Special emphasis is given on the data from fibre optics, which offers an advantage due to their spatially continuous nature. The data show a clear development of shaft friction with the applied load and also some unexpected pile–soil slip within two of the soil layers, which is attributed to the development of a filter cake due to the long construction time. Relevant finite-element analyses are also conducted in an attempt to further understand the mechanisms of pile–soil slip, which highlight its importance in predicting the vertical displacements. Finally, some comments are included on the observed behaviour of the founding chalk layer.