BBC1’s latest Sunday-night drama The Last Post, about a British military base in Aden in 1965, feels like a programme on a mission: that mission being to avoid getting shouted at by either the Guardian or the Daily Mail. To this (possibly doomed) end, it goes about its business very gingerly, with an almost pathological devotion to balance, and a safety-first reliance on the trusty methods of the well-made play, where each scene makes a single discrete point and the characters are as carefully differentiated as the members of a boy band.