To me this is Billy remembering a relationship with someone who was more patriotic / nationalistic than he was (not to any great degree, just more than him). Maybe this difference caused the breakup as he didn't understand her patriotism? With the distance of time he's come to realise it was just her point of view and can't even remember the specifics (the weather or battle of Agincourt?).
Maybe I'm thinking too much about the Agincourt line though as I did think that that battle took place on St Swithin's day, but in fact it was St Crispin's day. St Swithin's day is often associated with the weather but apparently it can also be used to refer to something that never gets completed and perhaps that is what is meant here?
To me this is Billy remembering a relationship with someone who was more patriotic / nationalistic than he was (not to any great degree, just more than him). Maybe this difference caused the breakup as he didn't understand her patriotism? With the distance of time he's come to realise it was just her point of view and can't even remember the specifics (the weather or battle of Agincourt?). Maybe I'm thinking too much about the Agincourt line though as I did think that that battle took place on St Swithin's day, but in fact it was St Crispin's day. St Swithin's day is often associated with the weather but apparently it can also be used to refer to something that never gets completed and perhaps that is what is meant here?