Erythemally-weighted ultraviolet (UV<i><sub>ery</sub></i>) levels measured over southern England, during anticyclonic weather between 30 April and 2 May, 1997, were almost 50 higher than normally expected for clear skies and were similar to mid-summer values for the first time since measurements began in 1990. Investigation of this episode suggests that a combination of both meteorological and chemical effects were responsible for generating record low ozone amounts for the time of year. Further, comparisons between the A band ultraviolet (315 to 400 nm wavelength) amounts, and radiative calculations confirm that the high UV<i><sub>ery</sub></i> was primarily due to the reduction in total ozone. These results are contrasted with a similar period for 1998, in which near climatological ozone amounts were measured. The prospects for enhanced UV<i><sub>ery</sub></i> levels in future years are briefly reviewed in the light of expected increases in stratospheric halogen levels and greenhouse gases.<br><br><b>Key words. </b>Atmospheric composition and structure (middle atmosphere · composition and chemistry) · Meterology and atmospheric dynamics (middle atmosphere dynamics; radiative processes)