MUSE spectra of GS551 (coral), showing AGN-ionised lines, according to UV diagnostics (Fig. 12). These spectra were obtained by integrating over the regions at S/N > 4 in Fig. 2; for visual purposes, the LAE2 spectrum was shifted, as labelled. The zoom-in insets show the same spectra in the vicinity of the lines used in the UV diagnostics, together with 1σ errors for the LAE2 spectrum (green curve, mostly highlighting the position of strong sky line residuals).