  I show that strong bars can grow in galactic discs, even when the latter are
immersed in haloes whose mass within the disc radius is comparable to, or
larger than, the mass of the disc. I argue that this is due to the response of
the halo and in particular to the destabilising influence of the halo resonant
stars. Via this instability mechanism the halo can stimulate, rather than
restrain, the growth of the bar.
