Flux calibrated and continuum subtracted spectra of 2I/Borisov obtained with the INT and WHT through a 2″ × 8″ aperture centred on the comet. The spike around 435 nm in the October 13 spectrum is a noise feature. The bottom plot shows spectra of two comets observed at similar heliocentric distances as 2I: 67P/Churyumov-Gerasimenko (from Opitom et al. 2017, r_h = 2.36 au), a Jupiter Family comet with a CN production rate similar as 2I and for which C₂ was not detected at that distance, and C/2013 US10 (Catalina) (from Opitom 2016, r_h = 2.30 au), a typical very active long-period comet, for which both C₂ and C₃ were detected. Those spectra have both been arbitrarily scaled on the y-axis.