  We present very high resolution hydrodynamical simulations of accretion discs
in black hole X-ray binaries accreting near the Eddington limit. The results
show that mass loss, irradiation and tidal interactions all have a profound
effect on the observed behaviour of long period X-ray transients. In
particular, the interplay of all of these effects in the outer regions of the
accretion disc is able to drive long time-scale (weeks to years) variability is
these objects, and is a possible origin for some of the extreme variability of
GRS1915+105.
