Top: CMDs of fields NW4, NW5, and NW6 in radial bins of width 10′ . The radial angular distance from the M 33 centre is displayed in the top-left corner of each plot. The isochrone that best fits the RGB slope and colour is also shown. The corresponding metallicity and age are indicated in the top-left corner of each panel. Bottom: CMDs in radial bins at angular distances greater than 80′ including stars in field NW7. The stellar populations in these regions appear to be older and more metal-poor with an average metallicity [M/H]  = −1.3.