J − H versus H colour–magnitude diagram of Wd1. The colour scale shows the probability for a star to be a cluster member based on the field star subtraction method described in the text. We note that the population of red clump stars erroneously characterised as high probability cluster members. This is due to the small differences in extinction along the line of sight. Overplotted is a reddened (by A_k = 0.92) Siess et al. (2000) 4 Myr isochrone shifted to a distance of 4.8 kpc. The (reddened) MS from Marigo et al. (2008) is shows as the dotted line.