g − i colour plotted versus redshift for the spectroscopically confirmed UCMGs in KiDS (∼100, T18; S20). The relic candidates, targets of the XSH INSPIRE LP, are plotted as green points. The three objects, which are the focus of this study, are plotted as magenta diamonds. Blue points are UCMGs from T18 and S20 consistent with younger stellar ages. Two out of the three confirmed relics of F17 are plotted as yellow triangles (colours are taken from the SDSS DR16). Lines show single-burst old stellar population models (Bruzual & Charlot 2003) with solar (Z = 0.02, solid lines), sub-solar (Z = 0.008, dotted), and super-solar (Z = 0.05, dashed) metallicity and ages of 12 Gyr (black) and 8 Gyr (red).