  We discuss the propagation of light in the C-metric. We discover that null
geodesics admit circular orbits only for a certain family of orbital cones.
Explicit analytic formulae are derived for the orbital radius and the
corresponding opening angle fixing the cone. Furthermore, we prove that these
orbits based on a saddle point in the effective potential are Jacobi unstable.
This completes the stability analysis done in previous literature and allows us
to probe into the light bending in a two black hole metric. More precisely, by
constructing a suitable tetrad in the Newmann-Penrose formalism, we show that
light propagation in this geometry is shear-free, irrotational, and a light
beam passing by a C-black hole undergoes a focussing process. An exact analytic
formula for the compression factor $\theta$ is derived and discussed.
Furthermore, we study the weak and strong gravitational lensing when both the
observer and the light ray belong to the aforementioned family of invariant
cones. In particular, we obtain formulae allowing to calculate the deflection
angle in the weak and strong gravitational lensing regimes.
