KiDS+2dFLenS+GAMA: Testing the cosmological model with the $E_{\rm G}$
  statistic
  We present a new measurement of $E_{\rm G}$, which combines measurements of
weak gravitational lensing, real-space galaxy clustering and redshift space
distortions. This statistic was proposed as a consistency test of General
Relativity (GR) that is insensitive to linear, deterministic galaxy bias and
the matter clustering amplitude. We combine deep imaging data from KiDS with
overlapping spectroscopy from 2dFLenS, BOSS DR12 and GAMA and find $E_{\rm
G}(\overline{z}=0.267)=0.43 \pm 0.13$ (GAMA), $E_{\rm
G}(\overline{z}=0.305)=0.27 \pm 0.08$ (LOWZ+2dFLOZ) and $E_{\rm
G}(\overline{z}=0.554)=0.26 \pm 0.07$ (CMASS+2dFHIZ). We demonstrate that the
existing tension in the value of the matter density parameter hinders the
robustness of this statistic as solely a test of GR. We find that our $E_{\rm
G}$ measurements, as well as existing ones in the literature, favour a lower
matter density cosmology than the Cosmic Microwave Background. For a flat
$\Lambda$CDM Universe and assuming GR, we find $\Omega_{\rm
m}(z=0)=0.25\pm0.03$. With this paper we publicly release the 2dFLenS dataset
at: \url{http://2dflens.swin.edu.au}.
