  We quantify the relative importance of environmental quenching versus
pre-processing in $z\sim1$ clusters by analysing the infalling galaxy
population in the outskirts of 15 galaxy clusters at $0.8<z<1.4$ drawn from the
GOGREEN and GCLASS surveys. We find significant differences between the
infalling galaxies and a control sample; in particular, an excess of massive
quiescent galaxies in the infalling region. These massive infalling galaxies
likely reside in larger dark matter haloes than similar-mass control galaxies
because they have twice as many satellite galaxies. Furthermore, these
satellite galaxies are distributed in an NFW profile with a larger scale radius
compared to the satellites of the control galaxies. Based on these findings, we
conclude that it may not be appropriate to use 'field' galaxies as a substitute
for infalling pre-cluster galaxies when calculating the efficiency and mass
dependency of environmental quenching in high redshift clusters. By comparing
the quiescent fraction of infalling galaxies at $1<R/R_{200}<3$ to the cluster
sample ($R/R_{200}<1$) we find that almost all quiescent galaxies with masses
$>10^{11}M_{\odot}$ were quenched prior to infall, whilst up to half of lower
mass galaxies were environmentally quenched after passing the virial radius.
This means most of the massive quiescent galaxies in $z\sim1$ clusters were
self-quenched or pre-processed prior to infall.
