  We calculate the effect of illumination of dwarf nova accretion discs by
radiation from a hot, central, white dwarf. We show that only for very hot
white dwarfs (Teff ~ 40 000$ K) the inner region of quiescent dwarf nova discs
are partially depleted so that the delay between the rise to outburst of the
optical and UV fluxes would be increased as suggested recently by King (1997).
This depletion, however, must create several small outbursts between main
outbursts, contrary to observations. Lower white dwarf temperatures may cause
the outburts to be of the `inside-out' type removing the UV delay. We conclude
that white dwarf irradiation of dwarf nova discs is not very efficient for
example because the UV radiation from the hot white dwarf does not penetrate
deep enough in the disc atmosphere. The total ablation of the inner disc by
e.g. evaporation (possibly related to illumination) appears to be a very
promising possibility, accounting for both the EUV delay and the general
lightcurves properties.
