While filming the Orange walk scenes, the cast and crew were occasionally met with opposition from angry locals who were throwing objects towards the parade.
The Orange Order is a conservative British unionist organisation with links to Ulster loyalism. As a strict Protestant society, it does not accept non-Protestants as members. Marches through mainly Catholic and Irish nationalist neighborhoods are controversial and have often led to violence.
While driving out of Derry there is a lanyard of yellow and green around the rear view mirror in Gerry's car, these are colours for Donegal in GAA. Tommy Tiernan who plays Gerry was born in Donegal.
Turning a member of the IRA in to the police was not an option. They would also have to testify. It was a death sentence and probably a brutal one, The family might not have escaped either. The Protestant paramilitaries did the same.