The Maze, where Billy Wright was shot dead, houses some of Northern Ireland's most notorious prisoners. This is the second major lapse in three weeks. On December 10th, IRA killer Liam Averill escaped dressed as a woman. Sentenced to life imprisonment for the murder of two Protestants shortly before the IRA announced its 1994 ceasefire, he was smuggled out of prison with a group of women and children attending a Christmas party.
In March, a 40ft tunnel seven feet underground, fitted with electric lighting, was found leading from H-block 7, where IRA inmates are held. It had breached the block's perimeter wall and was 80ft short of the outside wall.
The following month a British inquiry into the incident found that the paramilitaries controlled the blocks. Sir Patrick Mayhew, the then Northern Ireland Secretary, admitted that, through intimidation, paramilitary prisoners had over a number of years "in effect gained control within the wings to which they were confined". He added: "Recently searches have been carried out only infrequently." It was reported then that security would be tightened.
There are still reports that behind the walls and wire fences, hundreds of IRA and loyalist prisoners enjoy a relaxed regime where cells are unlocked 24 hours a day and they talk freely on mobile phones.
Prison officers are said to face death threats and constant intimidation. More than 20, most of them from the Maze, have been murdered during the Troubles, sometimes after they were recognised by former prisoners.
The prison was the scene of the so-called dirty protests in the 1970s, when IRA prisoners refused to wash, wore only blankets and smeared their own excreta on cell walls.
In 1981, Bobby Sands and nine other republican inmates starved themselves to death in hunger strikes.
In 1983, 38 IRA prisoners staged a mass breakout.
In his report into the escape, Sir James Hennessy, then Chief Inspector of Prisons, concluded that only "inhuman and unacceptable methods" could guarantee absolute security.
Commentators regard the reported relaxation of the regime as dating from the early 1980s, with provision of more favourable treatment as a tactic to improve the political climate outside.