We have used the Hipparcos satellite colour magnitude diagram to determine the age of the Galactic disc .
We first measure the metallicities of the clump stars using DDO photometry ( Høg & Flynn 1997 ) .
We then use isochrones covering the range of disc metal abundance and the morphology of the turn off and sub-giant region to place constraints on the minimum age of the Galactic disc .
We derive a minimum age of 11 \pm 2 Gyr .
In conjunction with the new ages derived for globular clusters using the same method ( Jimenez et al 1996 ) our results indicate that the delay between the formation of the halo and the disc was up to 2-3 Gyr .
We show that a Reimers mass-loss law is sufficient to explain the morphology of the red clump .