Knowledge of the structure and kinematics of gas around supermassive black holes is vital to understanding accretion and thus AGN feedback, but the vast majority of AGN project sizes too small to be directly resolvable. Consequently the most powerful tool available is reverberation mapping, which substitutes time resolution for spatial resolution. In particular, in recent years, Swift has made a breakthrough in reverberation mapping, by measuring X-ray/UV/optical time lags that map out scales of the accretion disc, but curiously, the results seem to suggest a departure from the standard picture of a compact X-ray corona irradiating a geometrically thin disc. Here we present new results of the 100-day Swift, NICER and Las Cumbres Observatory reverberation mapping campaign of the local Seyfert Mrk 335. Despite being in an anomalously low X-ray state, the UV to optical lags follow the canonical wavelength dependence. We discuss these results in the context of the growing sample of Seyfert galaxies with high-cadence monitoring, and how they reveal new constraints on the circumnuclear environments of supermassive black holes.