United Ireland: why is it not on cards despite Sinn Féin success?

Sinn Fein has called for debate on Irish unification, but many obstacles exist to a referendum on the issue

Sinn Fein hailed its first victory in a Northern Ireland assembly election as a defining moment for the British-controlled region and called for a debate on a united Ireland.

The party's president, Mary Lou McDonald, had a simple message for unionists on Saturday, telling them: Don't be scared, the future is bright for us all."