  We classify all higher-order generalised Einstein-Maxwell Lagrangians that
include terms linear in the curvature tensor and quadratic in the derivatives
of the electromagnetic field strength tensor. Using redundancies due to the
Bianchi identities, dimensionally dependent identities and boundary terms, we
show that a general Lagrangian of this form can always be reduced to a linear
combination of only 21 terms, with coefficients that are arbitrary functions of
the two scalar invariants derived from the field strength. We give an explicit
choice of basis where these 21 terms include 3 terms linear in the Riemann
tensor and 18 terms quadratic in the derivatives of the field strength.
