A former loyalist paramilitary commander turned supergrass has pleaded guilty to 200 terrorist offences, including five murders.
Gary Haggarty, the ex-chief of the Ulster Volunteer Force's notorious north Belfast unit, admitted the litany of crimes as part of his deal with the State to give evidence against fellow terrorists.
As well as the five murders, the 45-year-old, who is currently in protective custody, admitted five attempted murders, including against police officers; 23 counts of conspiracy to murder; directing terrorism; and membership of a proscribed organisation, when he appeared before a judge at Belfast Crown Court.
Haggarty, who worked as a police informant during the Troubles, was interviewed more than 1,000 times by detectives in one of the biggest and most complex cases ever undertaken in Northern Ireland.
The catalogue of offences stretch over a 16-year period from 1991 to 2007 and include the loyalist murders of John Harbinson, Sean McParland, Gary Convie, Eamon Fox and Sean McDermott.
The lengthy charge sheet also includes aiding and abetting murder, kidnap, possession of firearms, ammunition and explosives as well as hijacking, false imprisonment, arson, intimidation and conspiracy to riot.
Haggarty is expected to receive a heavily reduced sentence in exchange for his cooperation with the authorities.
He could well walk free, given he has already served three years in custody - the equivalent of a six-year sentence.
Sentence is expected to be passed later in the year.
Solicitor Niall Murphy speaking outside court:
In the interim prosecutors will decide how to proceed with the evidence he has provided.
It is understood Haggarty has made allegations against 14 fellow loyalists, for crimes including four murders.
He has also given evidence in relation to alleged criminality by two former Royal Ulster Constabulary (RUC) Special Branch handlers who worked with him when he was an informer.
The content of his interviews amounts to 23,000 pages of transcribed evidence.
There was a significant police presence in and around the court for the high-profile arraignment hearing.
Haggarty, who is believed to be living at a secret location outside Northern Ireland, was escorted into court through a side door by two specialist police officers.
He was initially arrested in 2009 and charged with the murder of Mr Harbinson.
He then indicated his willingness to turn state's witness and subsequently signed an agreement to become an assisting offender under the terms of the Serious Organised Crime and Police Act (Socpa).
The terror boss, whose address was formally recorded on the indictment sheet as care of a Belfast police station, stood in the dock dressed in a grey suit during the hearing before judge Mr Justice Treacy.
He said 'guilty' as each charge was put to him, the majority in short form summary.
Relatives of some of his victims watched on from the public gallery of the court.
Detective Superintendent Richard Campbell, from the PSNI's Serious Crime Branch, said the guilty pleas marked a "milestone" for the victims and their families.
"Our thoughts today are first and foremost with the victims and their families especially those murdered by Gary Haggarty; namely Sean McParland who was shot in front of his young grandchildren in February 1994 and died as a result 8 days later; Eamon Fox and Gary Convie who were shot dead as they ate their lunch in their car in May 1994, Sean McDermott who was shot dead in August 1994 and John Harbinson who was attacked on May 18 1997," he said.
"Gary Haggarty has also pleaded guilty to aiding and abetting the murder of Peter McTasney, who was shot dead in his home in front of his three-year-old daughter in February 1991.
"It has been a very long, arduous and painful process for these families and I hope today's proceedings have made a significant contribution to the process of ultimately bringing closure to all the families of the victims of Mount Vernon (North Belfast estate) UVF during that time.
"The PSNI remains committed to moving forward and working with the PPS (Public Prosecution Service) in relation to the next stages of the investigation into Mount Vernon UVF and others who were involved with committing these offences.
"My detectives have worked hard over the last seven years to bring justice. I understand the frustrations of the families over the length of time this has taken but I have always said that it was important to take the time to get it right."