If Scappaticci is charged, then a lot of people on both sides of the Irish Sea will be nervous
Just 24 hours after the dirty war was exposed in the Gary Haggarty trial, another high-profile informer has hit the headlines with the arrest of Freddie Scappaticci.
Haggarty was convicted of five murders, five attempted murders, 23 conspiracies to murder and numerous other crimes, but he's still a small fish compared to 'Scap'.
The death and destruction the loyalist brought to his own community, and to Catholics who had the misfortune to fall into his path, is clear.
But as leader of the Mount Vernon UVF, his influence was local.
So far Scap is the most senior exposed British agent in the IRA, playing a key role in the organisation for two decades.
He knows its leadership's darkest secrets. If he is charged, a lot of people on both sides of the Irish Sea will be very nervous.
Senior figures in the intelligence world, and the political masters in London to whom they reported, will be distinctly uneasy.
The Army Council members on whose instructions he acted will also have reason for serious concern.
Yet if he is charged, it's difficult to see Scap then deciding to turn supergrass and spilling secrets.
A 72-year-old with children and grandchildren living in west Belfast is unlikely to take such a drastic course of action.
Although the relatives of his alleged victims were reportedly given prior warning of his arrest, his detention - like the man himself - remains shrouded in secrecy. He is being questioned by detectives at an undisclosed location about allegations of murder, kidnap and torture. We don't know if it is based on old or new evidence. He has always denied being Stakeknife, the codename given to him by his handlers.
The arrest will give hope to the victims' families. They have enormous faith in Bedfordshire Chief Constable Jon Boutcher, who is leading Operation Kenova.
With a team of 48 detectives and a £35m budget, he has pledged to leave no stone unturned and to follow the evidence no matter where it leads.
"My principal aim in taking responsibility for this investigation is to bring those responsible for these awful crimes, in whatever capacity they were involved, to justice," he said in June 2016.
But no matter how sincere those words, the experiences of Stalker, Sampson and Stevens suggests there are real limits on how far well-meaning English policemen can go in exposing the rotten core of the State's dirty war.
Scap began working for military intelligence in 1976. He was recruited by a soldier called Peter Jones. Numerous theories have emerged as to why he chose to betray the IRA, but none so far is definitive. He was reportedly paid £80,000 a year for his work.
While the Provisionals now attempt to minimise his significance and distance him from their top brass, in his role in the nutting squad he worked hand in glove with Army Council leaders.
While he was not involved in the kitchen cabinet of figures in Sinn Fein and the IRA deciding political policy, he was still integral to the peace process and the British strategy.
Running internal security, his ability to inflict havoc on the Provisionals' structural integrity and military capacity was unparalleled. He was in the ideal strategic position to emasculate the IRA and allow the republican movement to be taken in the direction of constitutional politics.
He could get rid of informers who had passed their sell-by-date, protect and promote others who remained valuable, and cast security doubts over hawkish members in the ranks.
No wonder the former commanding officer of the Army in Northern Ireland, General Sir John Wilsey, sang his praises.
Military intelligence whisteblower Ian Hurst secretly recorded Sir John talking about Scap. "He was a golden egg, something that was very important to the Army. We were terribly cagey about Fred," he said.
Without Hurst's courageous efforts, we wouldn't even know of Stakeknife and those dark secrets. For it was not just the British establishment who wanted to keep the door shut on the truth.
The Provos did everything possible to discredit efforts to expose Scap as a British agent in 2003.
As the west Belfast man proclaimed his innocence, the Sinn Fein machine swung into action.
Martin McGuinness denounced the "nameless, faceless securocrats" making outrageous accusations against an innocent grandad. Gerry Adams said he believed Scap and rebuked journalists pursuing the story.
Ex-IRA member Anthony McIntyre was scathing in his response. "Like the Catholic Church in sex abuse cases, the IRA leadership acted to protect themselves and their own reputations by covering up the truth about Stakeknife," he said.
"The IRA leadership who put people down holes for the slightest misdemeanour, effectively colluded with a top British agent to cover up his nefarious role in the deaths of Irish citizens."