It's not realy about a battle 300 years ago. It's about the present and the future. The Battle of the Boyne is a symbol.

The reality of the Battle of the Boyne, as has been pointed out is different from the myth. The Pope authorised a Te Deum in Rome in thanksgiving for the victory of William. There were more Catholic troops in Williams's army than there were Protestants. And of course the Orange Order wasn't set up until more than a hundred years later, and Protestants were among the leading Irish Republicans in 1798.

But the 12th isn't really anything to do with history as it happened. It's like in any family quarrel, all kinds of half forgotten events from the past get pulled out and brandished, but that's not what it's about. In a different atmosphere the same episodes would very likely be recalled as a way of binding people together - "well, if we got over that, we can get over anything".

And that's how it'll be with the Battle of the Boyne and a lot of more recent happenings, when peace has really come. "When", not "if".