evidence: The backstop is an insurance policy to avoid a hard border between Northern Ireland and the Republic if a free trade deal between the UK and EU is not reached by the end of the transition period. [...] Northern Ireland's Democratic Unionist Party has made its opposition to the backstop clear and has been pressing Mrs May to secure changes to it. Indeed, some British MPs want it scrapped altogether. They oppose it because they fear it will weaken the constitutional integrity of the Union - as Northern Ireland would be treated differently to the rest of the UK by following different rules and regulations if the backstop was to come into effect.