  Stars within 0.1 pc of the supermassive black hole Sgr A* at the Galactic
centre are expected to encounter a cluster of stellar-mass black holes (BHs)
that have segregated to that region. Some of these stars will scatter off an
orbiting BH and be kicked out of the Galactic centre with velocities up to
~2000 km/s. We calculate the resulting ejection rate of hypervelocity stars
(HVSs) by this process under a variety of assumptions, and find it to be
comparable to the tidal disruption rate of binary stars by Sgr A*, first
discussed by Hills (1988). Under some conditions, this novel process is
sufficient to account for all of the hypervelocity B-stars observed in the
halo, and may dominate the production rate of all HVSs with lifetimes much less
than the relaxation time-scale at a distance ~2 pc from Sgr A* (>~ 2 Gyr).
Since HVSs are produced by at least two unavoidable processes, the statistics
of HVSs could reveal bimodal velocity and mass distributions, and can constrain
the distribution of BHs and stars in the innermost 0.1 pc around Sgr A*.
