  The gravitationally lensed quasar APM 08279+5255 has the fastest claimed wind
from any AGN, with velocities of 0.6-0.7c, requiring magnetic acceleration as
special relativisitic effects limit all radiatively driven winds to v<0.3-0.5c.
However, this extreme velocity derives from interpreting both the narrow and
broad absorption features in the X-ray spectrum as iron absorption lines. The
classic ultrafast outflow source PDS 456 also shows similar absorption systems,
but here the higher energy, broader feature is generally interpreted as an
absorption edge. We reanalyse all the spectra from APM 08279+5255 using a full
3-dimensional Monte Carlo radiative transfer disc wind model for the ionised
wind at 0.1-0.2c, together with complex absorption from lower ionisation
material, and find that this is a better description of the data. Thus there is
no strong requirement for outflow velocities beyond 0.2c, which can be powered
by radiation driving. We show that UV line driving is especially likely given
the spectral energy distribution of this source which is intrinsically UV
bright and X-ray weak. While the peak of this emission is unobservable, it must
be luminous enough to power the observed hot dust, favouring at least moderate
black hole spin.
