Over the course of the day , up to 30,000 people were expected to join the Ulster Covenant parade , held to mark the 100th anniversary of the signing of a pro-union document which helped shape Northern Ireland 's history . Thousands of police are deployed in Belfast to prevent possible outbreaks of violence . The march marks the centenary of the signing of the pro - union Ulster Covenant . Up to 30,000 people are expected to take part in the march . tensions have been high this summer between Catholics and Protestants in the city .
Thousands of police are deployed in Belfast to prevent possible outbreaks of violence . The march marks the centenary of the signing of the pro - union Ulster Covenant . Up to 30,000 people are expected to take part in the march . tensions have been high this summer between Catholics and Protestants in the city .