  During its first 4 months of taking data, Advanced LIGO has detected
gravitational waves from two binary black hole mergers, GW150914 and GW151226,
along with the statistically less significant binary black hole merger
candidate LVT151012. We use our rapid binary population synthesis code COMPAS
to show that all three events can be explained by a single evolutionary channel
-- classical isolated binary evolution via mass transfer including a common
envelope phase. We show all three events could have formed in low-metallicity
environments (Z = 0.001) from progenitor binaries with typical total masses
$\gtrsim 160 M_\odot$, $\gtrsim 60 M_\odot$ and $\gtrsim 90 M_\odot$, for
GW150914, GW151226, and LVT151012, respectively.
