  We use data from the Isaac Newton Telescope Wide Field Camera survey of M31
to determine the surface brightness profile of M31 along the south-east minor
axis. We combine surface photometry and faint red giant branch star counts to
trace the profile from the innermost regions out to a projected radius of 4
degrees (~55 kpc) where the V-band surface brightness is 32 mag per square
arcsec; this is the first time the M31 minor axis profile has been mapped over
such a large radial distance using a single dataset. We confirm the finding by
Pritchet & van den Bergh (1994) that the minor axis profile can be described by
a single de Vaucouleurs law out to a projected radius of 1.4 degrees or ~20
kpc. Beyond this, the surface brightness profile flattens considerably and is
consistent with either a power-law of index -2.3 or an exponential of
scalelength 14 kpc. The fraction of the total M31 luminosity contained in this
component is ~2.5%. While it is tempting to associate this outer component with
a true Population II halo in M31, we find that the mean colour of the stellar
population remains approximately constant at V-i~1.6 from 0.5-3.5 degrees along
the minor axis. This result suggests that the same metal-rich stellar
population dominates both structural components.
