The Britain of Alex Garland’s 28 Years Later films might have been infested by man-eating zombies since 2002, but its handful of surviving centrist dads are still valiantly keeping the Blairite flame alive. Foremost among them – and the de facto star of this grimmer, grimier second chapter – is Ralph Fiennes’s Dr Ian Kelson, a former GP who’s either gone completely mad or is the only sane man within a hundred miles.