A coroner has expressed frustration at the lack of progress in the case of a dissident republican who killed himself in police custody.
Real IRA man John Brady (40) was found dead at Strand Road police station in Londonderry in October 2009.
The case is shrouded in controversy over allegations that two officers from the PSNI's C3 unit - formerly known as Special Branch - visited the veteran republican on three separate occasions before his death.
Judge Brian Sherrard told a preliminary hearing at Belfast Coroner's Court: "It is a matter of regret that we have not managed to make more progress than we have done."
Rumours of C3 involvement have led to speculation Mr Brady may have been subjected to a bid to turn him into an informer before he killed himself in a consultation room.
The Police Ombudsman examined these claims and found no evidence to support them.
The ombudsman said two intelligence officers did attempt to gain access to Mr Brady but were turned away by custody staff - a finding investigators said was substantiated by CCTV footage.
The court also heard that some security documents related to the high-profile case are so sensitive, the coroner's legal representatives have not been allowed to see them.
Judge Sherrard revealed he met police on Wednesday to look at the papers personally, adding: "As it turns out the counsel instructed does not have sufficient clearance."
Mr Brady was jailed during the Troubles for murdering a policeman and had been arrested in Strabane while on parole on suspicion of assault. A PSNI barrister accepted an appeal from the coroner that the matter be addressed urgently.