Hybrid Natural Inflation
  We construct two simple effective field theory versions of {\it Hybrid
Natural Inflation (HNI)} that illustrate the range of its phenomenological
implications. The resulting inflationary sector potential,
$V=\Delta^4(1+a\cos(\phi/f))$, arises naturally, with the inflaton field a
pseudo-Nambu-Goldstone boson. The end of inflation is triggered by a waterfall
field and the conditions for this to happen are determined. Also of interest is
the fact that the slow-roll parameter $\epsilon$ (and hence the tensor $r$) is
a non-monotonic function of the field with a maximum where observables take
universal values that determines the maximum possible tensor to scalar ratio
$r$. In one of the models the inflationary scale can be as low as the
electroweak scale. We explore in detail the associated HNI phenomenology,
taking account of the constraints from Black Hole production, and perform a
detailed fit to the Planck 2015 temperature and polarisation data.
