  We model the secular evolution of a star's orbit when it has a nearby binary
system. We assume a hierarchical triple system where the inter-binary distance
is small in comparison with the distance to the star. We show that the major
secular effect is precession of the star's orbit around the binary system's
centre of mass. We explain how we can obtain this precession rate from the
star's radial velocity data, and thus infer the binary system's parameters. We
show that the secular effect of a nearby binary system on the star's radial
velocity can sometimes mimic a planet. We analyze the radial velocity data for
{\nu}-octantis A which has a nearby companion ({\nu}-octantis B) and we obtain
retrograde precession of (-0.86 \pm 0.02)\degree/yr. We show that if
{\nu}-octantis B was itself a double star, it could mimic a signal with
similarities to that previously identified as a planet of {\nu}-octantis A.
Nevertheless, we need more observations in order to decide in favor of the
double star hypothesis.
