  We study in detail the evolution of the 2015 outburst of GS 1354-64 (BW Cir)
at optical, UV and X-ray wavelengths using Faulkes Telescope South/LCOGT,
SMARTS and Swift. The outburst was found to stay in the hard X-ray state,
albeit being anomalously luminous with a peak luminosity of L$_{X} >$ 0.15
L$_{Edd}$, which could be the most luminous hard state observed in a black hole
X-ray binary. We found that the optical/UV emission is tightly correlated with
the X-ray emission, consistent with accretion disc irradiation and/or a jet
producing the optical emission. The X-ray spectra can be fitted well with a
Comptonisation model, and show softening towards the end of the outburst. In
addition, we detect a QPO in the X-ray lightcurves with increasing centroid
frequency during the peak and decay periods of the outburst. The long-term
optical lightcurves during quiescence show a statistically significant, slow
rise of the source brightness over the 7 years prior to the 2015 outburst. This
behaviour as well as the outburst evolution at all wavelengths studied can be
explained by the disc instability model with irradiation and disc
evaporation/condensation.
