Left: HMI image at 20:00 UT 13 April 2020, showing the magnetic field just before the cavity began to rise. The blue ‘X’ marks the location of the GCS approximated source region, whilst the red box marks the approximate location of the cavity that was observed at the solar limb. Right: corresponding AIA 193 Å image, with the GCS and cavity regions being highlighted as before. In both figures, the limb of EUVI-A is over-plotted as the white line.