Thursday’s Westminster election may produce huge surprises in Northern Ireland, but what will it produce in Britain post-Brexit? In matters Irish, most Westminster elections have had little impact. But every so often, they have had political life-changing consequences on Ireland, north and south, and henceforth a seminal impact on British-Irish relations.    Most famously a century ago, the 1918 Westminster election ended the Home Rule era, democratised the Irish revolution and launched the events that within a few years partitioned Ireland into two different states. More recently, the 1974 Westminster election returned 11 anti-Sunningdale Agreement Unionist members out of the twelve…