Despite speculation that nuclear activity in galaxies may be triggered by mergers and interactions, very little is known about the true nature of the link. I will present deep Gemini/GMOS imaging of powerful radio galaxies and quasars which reveal that ~80-85% of their galaxy hosts show signs of interactions at relatively high levels of surface brightness. The galaxy morphologies are consistent not only with the galaxies being observed at, or after, the time of coalescence of the nuclei in a galaxy merger, but also in the pre-coalescence phase of the merger, or following a close encounter between galaxies. This means that powerful AGN can be triggered at any stage of the interaction. By comparing with a control sample of quiescent ellipticals, we find that the percentage of morphological disturbance in PRGs greatly exceeds that found for quiescent ellipticals (~30%) when similar surface brightnesses are considered.