Upper panel: colour magnitude diagram of the innermost 2.5′ from the centre of Sgr, N from the Advanced Camera for Surveys/Hubble Space Telescope photometry of Siegel et al. (2007). The stars associated by Siegel et al. (2007) with a possible young population (or a population of BSS), a population with age ≃2.3 Gyr and [Fe/H] =−0.1, and a population with age ≃4–6 Gyr and [Fe/H] =−0.6, are highlighted in different tones of grey, from the palest to the darkest, respectively. Lower panel: the cumulative radial distribution of the three populations are plotted using the same tones of grey (moreover, continuous line: young/BSS population; short-dashed line: 2.3 Gyr population; long-dashed line: 4–6 Gyr population). The probability that the samples tracing the 2.3 Gyr and the 4–6 Gyr populations have the same radial distribution is reported.