Pin on disc wear tests on steel and alumina discs have been carried out using the NPL designed system which enables in situ monitoring of the wear and surface condition through the use of a line-scan camera microscope. In addition, the combination of a Linear Voltage Displacement Transformer (LVDT) and a non-contact optical aberration probe make it possible to monitor the wear of the disc and of the pin separately as the tests progresses. Accurately triggered optical micrographs acquired during the test are subsequently registered to produce videos showing the wear of the disc and the transport of debris along the scar. This enables the dynamics of the processes that take place at the contact interface to be visualised in real time during a test.When these techniques were applied to pin-on-disc wear tests with steel and alumina balls tested against alumina discs, insights were gained on the development of interfacial films as the tests proceeded. For the steel ball, these were formed from iron oxide that formed and reformed and moved across the wear surface, and for the alumina ball an interfacial layer was formed which filled depressions in the lapped surface of the alumina. These interfacial films had reduced aluminium content compared to the original alumina in the surface.