Very long-baseline interferometry with future radio telescopes will offer unprecedented imaging resolution. I demonstrate a glimpse of what this will offer strong gravitational lensing, with the analysis of H-ATLAS J090311.6+003906 (SDP.81), an exceptional example of long-baseline interferometry with the Atacama Large Millimeter/sub-millimeter Array. While this is an example of sub-mm, not radio, interferometry, it acts as the perfect substitute to demonstrate the potential currently offline radio instruments will offer. I first focus on analysis of SDP.81's lens, a massive elliptical galaxy, the emission of which appears invisible at sub-mm / radio wavelengths. This crucially allows an uncontaminated analysis of the sources light. In combination with optical HST data, this allows strong lens modeling to decouple the lens's light and dark matter mass distributions. This offers unique insight into the dark matter halo of an individual galaxy, which is both rotationally offset and rounder then its baryonic material. I then present reconstructed imaging of the sub-mm source, in which the high imaging resolution combined with the lensing magnification, reveals a dust-rich on-going major merger, within which individual star-forming clumps are resolved on sub 200 pc scales. I finish with an overview of what the next generation of radio telescopes will offer strong lensing, given facilities such as LOFAR and SKA are predicted to find in excess of 20000 radio lenses, a figure some two orders of magnitude above the total number of lenses discovered across all wavelengths.