evidence: But it includes a potential future pathway to a united Ireland through a referendum, also called a border poll. The text which in UK law says the Northern Ireland secretary "shall exercise the power [to call a referendum] if at any time it appears likely… that a majority of those voting would express a wish that Northern Ireland should cease to be part of the United Kingdom". [...] Unionist parties are strongly opposed to the Northern Ireland Protocol - the post-Brexit trading arrangement which in effect has created a trade border with the rest of the UK.