The arrests of two journalists over “stolen” documents have “grave implications for press freedom”, a court was told.

Conservative MP and former Brexit secretary David Davis joined award winning film makers Trevor Birney and Barry McCaffrey at Belfast High Court on Tuesday to support their legal challenge against the police.

The pair were arrested last year over the alleged theft of a police watchdog document that appeared in their film No Stone Unturned on the murders of six men in Loughinisland, Co Down, in 1994.

They remain under live police investigation and are on bail.

The 2017 film broke new ground by naming the suspects it said were involved in the Ulster Volunteer Force (UVF) killings of six Catholic men who were gathered in a village pub watching the Republic of Ireland play a World Cup football match on TV.

The men are taking a judicial review against the execution of the police search warrant.

Journalistic documents, computers, notebooks, files and digital material seized by police when they raided their film production company - Fine Point - were bagged and sealed after lawyers secured an interim injunction preventing detectives examining them pending the hearing of the legal challenge.