  Natural inflation relies on the existence of an axion decay constant which is
super-Planckian. In string theory only sub-Planckian axion decay constants have
been found in any controlled regime. However in field theory it is possible to
generate an enhanced super-Planckian decay constant by an appropriate aligned
mixing between axions with individual sub-Planckian decay constants. We study
the possibility of such a mechanism in string theory. In particular we
construct a new realisation of an alignment scenario in type IIA string theory
compactifications on a Calabi-Yau where the alignment is induced through
fluxes. Within field theory the original decay constants are taken to be
independent of the parameters which induce the alignment. In string theory
however they are moduli dependent quantities and so interact gravitationally
with the physics responsible for the mixing. We show that this gravitational
effect of the fluxes on the moduli can precisely cancel any enhancement of the
effective decay constant. This censorship of an effective super-Planckian decay
constant depends on detailed properties of Calabi-Yau moduli spaces and occurs
for all the examples and classes that we study. We expand these results to a
general superpotential assuming only that the axion superpartners are fixed
supersymmetrically and are able to show for a large class of Calabi-Yau
manifolds, but not all, that the cancellation effect occurs and is independent
of the superpotential. We also study simple models where the moduli are fixed
non-supersymmetrically and find that similar cancellation behaviour can emerge.
Finally we make some comments on a possible generalisation to axion monodromy
inflation models.
