@tfb
> their sense of Britishness has more to do with Scotland than England.
Mmm, not sure about that. There are a lot of N. Irish with Scottish ancestry, that's true. Their distinctiveness has become defined by their religion (Protestant), and for many it is Calvinist in nature, which is another Scottish historical link. However, nowadays their Britishness and politics is more to do with "Empire" & Brexit.
There is also a football angle, but that is a whole different topic.