The standard model of cosmology assumes that the universe is isotropic & homogeneous when averaged on large scales. The dipole anisotropy observed in the CMB is attributed to our peculiar (non-Hubble) motion, due to local inhomogeneities, wrt the cosmic rest frame in which the CMB is isotropic. There should then be a corresponding dipole in the distribution of high redshift sources. Using catalogues of radio sources & quasars we find that the observed dipole does not match what is expected. This challenges the standard assumption of the FLRW metric, and the consequent inference that the universe is dominated by a Cosmological Constant, aka dark energy.