I assumed it was about the Irish Troubles, actually. The reference to "the clan", "Londonderry nights" (Londonderry being one of the places traditionally fought over by the British and the Irish since way before the Troubles), "words were cried at night / in unforgiving tones" = sectarianism?, from there on it's pretty self-explanatory assuming this is right. VW have written about British conflicts before (Mansard Roof = the Falklands War), so it's possible.
I assumed it was about the Irish Troubles, actually. The reference to "the clan", "Londonderry nights" (Londonderry being one of the places traditionally fought over by the British and the Irish since way before the Troubles), "words were cried at night / in unforgiving tones" = sectarianism?, from there on it's pretty self-explanatory assuming this is right. VW have written about British conflicts before (Mansard Roof = the Falklands War), so it's possible.