Enhanced backscattering from a random medium resulting from interference is known as weak localisation. In the backscattered light three polarisation effects are observed: there is partial retention of polarisation, the polarised cone of enhanced backscattering is spatially anisotropic, and a slight enhancement is found in the depolarised light component. It is proved experimentally that the three effects are due to lower-order scattering contributions, and the effects are explained. A computer simulation of enhanced backscattering from a medium containing randomly distributed Rayleigh scatterers confirms this interpretation.