  The form of the inflationary potential is severely restricted if one requires
that it be natural in the technical sense, i.e. terms of unrelated origin are
not required to be correlated. We determine the constraints on observables that
are implied in such natural inflationary models, in particular on $r$, the
ratio of tensor to scalar perturbations. We find that the naturalness
constraint does not require $r$ to be lare enough to be detectable by the
forthcoming searches for B-mode polarisation in CMB maps. We show also that the
value of $r$ is a sensitive discriminator between inflationary models.
