  The decay constants of the heavy-light pseudoscalar mesons are studied in a
high statistics run using the Wilson action at $\beta=6.0$ and $\beta=6.2$, and
the clover action at $\beta=6.0$. The systematics of $O(a)$ discretisation
errors are discussed. Our best estimates of the decay constants are: $f_D$ =
218(9) MeV, $f_D/f_{Ds}$ = 1.11(1) and we obtain preliminary values for $f_B$.
