We report the first results obtained from a continuing programme of spectrophotometric monitoring of high luminosity active galactic nuclei (AGN). Analysis shows that significant emission line variations take place in high luminosity, high redshift objects. These variations occur on time-scales much shorter than those expected from photo-ionization models. These shorter time-scales can be explained if the optical and ultraviolet continuum is beamed towards the observer, leading to an anisotropic BLR and a selection effect in favour of cases in which the axis of this anisotropy is close to the line-of-sight.