Fractions of individual stellar populations identified in the HPMS samples. Top: raw fractions of the accreted, heated-disc, and LAHN populations, derived from Gaussian decomposition (Figs. 8–10). For the photometric sample, only the accreted component is shown, because the heated and LAHN populations cannot be separated based on photometric metallicity estimates alone. Bottom: normalised fractions of the heated and LAHN populations, scaled so that their combined contribution matches that derived from the photometric sample.