In political and peace negotiations there is always a 'back channel'; a way for one side to get a message to the other. There is usually a 'facilitator' and, in the case of the Sinn Fein/DUP contacts in 2004, this role fell to a journalist.
These things are always hidden, always deniable. The process is not meant to have a trail leading to its participants - the risk-takers in these secret contacts.
So, when I first asked the journalist and the DUP about all of this way back in 2005 when I was the BBC's security editor, their denials did not surprise me.
Their problem is: these things never stay secret. There are those who keep diaries and others who send cables. The jigsaw of information can be pieced together into a telling picture.
Does anyone really believe that there was not contact between Sinn Fein and the DUP back in 2004? Have they read the book by Jonathan Powell, who at the time was Prime Minister Tony Blair's chief of staff? And are they reading the cables released by WikiLeaks and published in this newspaper yesterday?
In particular, there is that US Embassy cable from 2006 reporting a conversation with then Irish foreign minister Dermot Ahern, in which he referred to "substantive direct contact" between Sinn Fein and the DUP dating back to 2004.
In that period, the Irish Government was reporting the detail of the contacts to the British Government. And, in 2005, when I asked the Irish Government about those contacts the previous year, there was no confirmation, but no denial either.
"In the 10 years that the Taoiseach has been involved in the peace process, a great number of people and parties have assisted in terms of progressing issues in Northern Ireland," an e-mailed response read. "It has not been our position to comment on these matters."
Sinn Fein was also careful in its response, given to me by Gerry Adams's aide Richard McAuley: "This story, like so many others at key points in the peace process, emanates from sources who are opposed to the peace process and is designed to create difficulties. Sinn Fein does not intend to engage in this negative agenda, which is about undermining the search for agreement."
So, Sinn Fein was also careful in its choice of words - neither confirming nor denying the suggested contacts. In terms of those involved, I had been given the names of Martin McGuinness and his then adviser, Aidan McAteer.
But, when I met Mr McGuinness on a number of occasions to discuss this, he looked straight through me. I heard something in his silence and believed that, if the reports were nonsense, he would tell me.
You have to place the contacts story in the context of 2004. For the DUP, this was their first time at the heart of the post-Good Friday Agreement negotiations.
For years, they had been able to spend most of their time condemning republicans - and now their only route to power was in a deal with Sinn Fein.
The British and Irish governments were key players in the negotiations and this was a period in which the DUP made one demand too many - that there should be photographic proof of decommissioning.
And a negotiation in which Ian Paisley made one speech too many - his belief that the IRA should be humiliated and should wear sackcloth and ashes.
His son, Ian jnr, wanted to make sure that moment was seen and heard. He called me on a Friday night when I was pushing a trolley round a supermarket and asked could I send a camera crew to the event at which his father was speaking the following night.
There was no discussion about what Paisley snr was going to say, but when it was heard, the potential of a deal began to crumble.
Republicans and others were struggling to make sense of what was happening; why this speech at this time? We, as journalists, had only part of the picture.
But those like McGuinness and key figures in the British and Irish governments who knew of the quiet, but "substantive and direct" contacts that were going on, must have been wondering about this loud speech thrown into the middle of things.
When I put the suggestion of contacts to the DUP, I got this response: "The party was not and is not involved in negotiations/meetings with Sinn Fein.
"The party leadership have not at any time sanctioned or had knowledge of any meetings at any level between anyone from Sinn Fein and anyone from the DUP or anyone acting on behalf of either or both. As no such meetings took place, the rest of your questions are not relevant."
It was a straight denial. No room for interpretation. But I believed the contacts story and believed the sources talking to me.
In 2005, there was not the confirming information that is now available and I knew this story was going to have wait. But I also knew it would not go away.
I wrote an e-mail to the BBC's head of news and current affairs at the time, Andrew Colman, saying: "As it stands, I think the story is just going to have to wait for another time."
That time presented itself in March 2008. It came back in the pages of Jonathan Powell's book, Great Hatred, Little Room. And it has returned again in the cables released to the Belfast Telegraph by WikiLeaks.
And it takes us back to what I said at the start of this article: in peace and political negotiations, these things happen. But they are always deniable.