Normalised spectra of β Pic at seven different epochs, focussing on three Fe II line series at 2400, 2600, and 1750 Å. Vertical blue lines emphasise the Fe II transitions that were used in our analysis and are listed in Table A.1. Other lines not used in this paper may also show cometary features, such as Fe II multiplets (e.g. 2344, 2750 Å) or lines from other species (e.g. Mn II at 2576, 2594 and 2606 Å).