Brightest cluster galaxies (BCGs) are some of the most massive galaxies in the Universe and are generally found at the centre of groups and clusters of galaxies. They show very low scatter in their absolute magnitudes and form their own luminosity function, separate from other galaxies in the cluster. These unique properties suggest that their origin must be environmentally dependent. I will present research examining the relationship between BCG stellar mass and that of their host halo over the widest range in host system mass and redshift. I will show that there is no evidence for evolution in this relationship between z ~ 0.1 and z ~ 0.8: BCG growth appears to be limited by the time-scale for dynamical friction at both these times, not proceeding according to the predictions of present semi-analytic models.