Sources say a lot of things. In the Belfast Telegraph on Monday, Brian Rowan quoted political sources as saying a Government probe had found that Martin McGuinness was not a British spy.
As the person telling the other side of the story I have to differ. Brian is a respected journalist and I have no doubt he is accurately reporting what his sources tell him.
But they would say that wouldn't they? Could a political source confirm whether a person is an agent? Could the source be Sinn Fein? If it is, what they're saying is hardly credible. Could it be a Minister of State? Surely not a civil servant?
Cast your mind back a few years to the exposure of Freddie Scappaticci, an event I played a role in. At the time, political and security sources were dismissive about his role - yet the same sources who are dismissive of McGuinness today are now prepared to confirm both Scappaticci's and Denis Donaldson's roles as agents.
The same sources who brief against the McGuinness allegations today also briefed in secret that Stake Knife had been spirited out of Northern Ireland and was safe. Today we know these stories were lies, designed to deflect attention from the real villains.
The agent was relaxed at home in comfort, enjoying the protection of Sinn Fein and, of course, the British Government. It seems some things never change.
I have a pretty good record on these things. And it's not as if I've previously gone out of my way to attack McGuinness. The evidence I gave to the Saville Inquiry three years ago - relying on my time as an Army intelligence operative in Derry - cleared him of being the gunman who fired the first shot on Bloody Sunday.
During that testimony, the inquiry kept reminding me not to name any agents. A policeman was sitting about three feet away from me. I'm sure they were afraid I was going to identify McGuinness at that stage.
The thing is I had suspicions about McGuinness being an agent at that stage, but I didn't see the proof until about two years ago. That's when I was given the transcript of Agent J118 talking to his handlers.
It's true the document doesn't name McGuinness as Agent J118, but my sources have confirmed that's him. I trust my sources, because the information fits.
We're back to relying on sources, but from what I'm being told by republicans, they are investigating McGuinness and consider it a genuine document. And the document is only one strand of it. The fact is that Martin McGuinness is a protected species.
The Government has for some time argued in public and in private to journalists that Martin McGuinness is a real hardline IRA activist who constantly requires reassurance that the political process can deliver real changes, the thrust of the argument being his standing as a military hawk within the IRA.
That doesn't hold up, and republicans know this. McGuinness has no real military credentials and to argue otherwise is simply wrong. Jim Cusack in this paper last week made the very valid point about him winding Derry down to a mute IRA threat well before the peace process took hold.
Martin McGuinness was never interned. He has lived most of his life in Derry in the same area, never feeling the need to use safe houses out of fear of arrest. He was never convicted of any terrorist related offences in the North of Ireland from 1970 through till 2006.
The Irish government is on the record as saying that in 2005 Martin McGuinness was still a member of the IRA ruling army council. Yet he avoided two supergrass trials between 1982 and '84 in his hometown of Derry. Over fifty people were arrested; both agents were willing and able to give evidence against him, but the police did not proceed or were not allowed to.
Martin McGuinness was never attacked by loyalist paramilitaries. Attacks were known to have been planned but all were frustrated by security forces.
Then there was Operation Taurus. Police mounted a huge operation against him and believed they had the required evidence to charge him with directing terrorism. But a leaked secret memo shows clear political interference in due process. McGuinness was specifically excluded from any charges being brought in respect to the Cook Report or the murder of Frank Hegarty.
Hegarty was an agent for the FRU, the Army unit I worked in. He was promoted by McGuinness in defiance of his own IRA Brigade Staff. I knew Hegarty - he was a nice fella but not the sharpest knife in the drawer.
Eamonn McCann, the well known Derry journalist, on American radio recently said Franko had confirmed to him his role within the IRA. Eamon made the point it was common knowledge in Derry that Frank Hegarty had been an ex-Stickie and that he had previously been caught passing information to the Army. He also said Hegarty was indiscreet and he was surprised that Hegarty got so high up in the IRA.
More to the point, so were a lot of IRA men. These same men today are providing material to the ongoing IRA investigation into Martin McGuinness, in part because Frank Hegarty led the security forces to a massive cache of Libyan arms.
I remain convinced of the case against Martin McGuinness and just like I was proved right with Freddie Scappaticci, the same will, in my opinion, hold true for Martin McGuinness. Of course, he could meet his accuser face to face and we could debate this issue in depth. We could let the public decide who is telling the truth.