Models of spectral ageing have become a commonly used tool in describing the observed spectrum of FR-II radio galaxy lobes and to determine the age of a source radiating through synchrotron emission. However, recent findings have called into question the validity of many assumptions used within these models.

In this talk, I present the latest results from investigations using LOFAR and the JVLA to determine the dynamics and energetics of nearby FR-II radio galaxies and their spectral structure on small spatial scales. Using broad bandwidth observations between MHz and GHz frequencies, we address the issue of which classical assumptions are likely to be unreliable and provide revised values for our sample. Through radio synchrotron / X-ray inverse-Compton modelling, we also constrain the magnetic field strength and provide improved estimates of the total energy content. I go on to discuss what impact these finding have on our understanding of FR-II galaxies and what questions must be addressed if we are to truly understand the underlying physics of these powerful radio sources and ultimately their impact of galaxy evolution as a whole.