  Iron line emission is common in the X-ray spectra of accreting black holes.
When the line emission is broad or variable then it is likely to originate from
close to the black hole. X-ray irradiation of the accretion flow by the
power-law X-ray continuum produces the X-ray 'reflection' spectrum which
includes the iron line. The shape and variability of the iron lines and
reflection can be used as a diagnostic of the radius, velocity and nature of
the flow. The inner radius of the dense flow corresponds to the innermost
stable circular orbit and thus can be used to determine the spin of the black
hole. Studies of broad iron lines and reflection spectra offer much promise for
understanding how the inner parts of accretion flows (and outflows) around
black holes operate. There remains great potential for XMM-Newton to continue
to make significant progress in this work. The need for high quality spectra
and thus for long exposure times is paramount.
