  Long-baseline neutrino oscillation experiments, in particular Deep
Underground Neutrino Experiment (DUNE) and Tokai to Hyper-Kamiokande (T2HK),
will lead the effort in the precision determination of the as yet unknown
parameters of the leptonic mixing matrix. In this article, we revisit the
potential of DUNE, T2HK and their combination in light of the most recent
experimental information. As well as addressing more conventional questions, we
pay particular attention to the attainable precision on {\delta}, which is
playing an increasingly important role in the physics case of the long-baseline
programme. We analyse the complementarity of the two designs, identify the
benefit of a programme comprising distinct experiments and consider how best to
optimise the global oscillation programme. This latter question is particularly
pertinent in light of a number of alternative design options which have
recently been mooted: a Korean second detector for T2HK and different beams
options at DUNE. We study the impact of these options and quantify the
synergies between alternative proposals, identifying the best means of
furthering our knowledge of the fundamental physics of neutrino oscillation.
