At which point apologies and recriminations are made, each blaming the other. Even that isn't going to escalate things to a war level. Again: dead member of the Royal Family in Irish waters, dead Ambassador and wife in Ireland, the UK embassy burned to the ground, long time suggestion/rumour of UK collusion with the largest terror attack on the island against Dublin and Monaghan... None of this triggered such an escalation, so why would a regrettable "accident" do so?
Wow didn't know about the ambassador. Gotta say losing an eye while fighting the Nazi's and responding by wearing a smoked glass monacle over the false replacement one is pretty bad ass.
But yeah I agree it's unlikely my scenario would result in war.
I mean wow the UK put up with a lot of shit from the Provo's over the years without going full bore.