Declan Harvey investigates why Northern Ireland is the only part of the UK to not allow same-sex couples to marry. With the recent 'yes' vote in the Republic of Ireland in favour of gay marriage and many other countries across Europe changing their laws to allow it, why is Northern Ireland different? We meet young gay people who say they're embarrassed and frustrated at their country's lack of progress and hear the strongly held arguments against change from the governing Democratic Unionist Party.