  We calculate the process $pp\to W^+W^-\to e^+ \nu_e \mu^-\bar{\nu}_\mu$ at
NLO QCD, including also effective field theory (EFT) operators mediating the
$ggW^+W^-$ interaction, which first occur at dimension eight. We further
combine the NLO and EFT matrix elements produced by GoSam with the
HERWIG7/MATCHBOX framework, which offers the possibility to study the impact of
a parton shower. We assess the effects of the anomalous couplings by comparing
them to top-mass effects as well as uncertainties related to variations of the
renormalisation, factorisation and hard shower scales.
