One more trip to the ravaged lands of Danny Boyle and Alex Garland’s infected UK, courtesy this time of new director Nia Dacosta. Iain MacLeod reviews the massively entertaining entry that brings Ralph Fiennes’ kindly Dr Kelson and Jack O’Connell’s evil Sir Jimmy Crystal face to face in a film which while only being released in the second week of January could end up being one of the best of the year.