Over a cup of coffee, we were discussing security and threats, and the intelligence source put the G8 summit into a much wider context and frame; a frame that stretched further than Northern Ireland to include the London Olympics and the Queen's historic visit to the Republic.
"Any big event generates more discussion," the source said. He meant what, in his trade, is called "chatter"; the type of conversations that intelligence officers listen in on and try to make sense of. Their task is to separate talk from intent – and, in their listening, to make assessments.
So, in the run-up to G8, the source is expecting "an increase in threat reports, but not necessarily an increased threat".
Given the world nature of this event, given those who will be present, anything that is heard in the eavesdropping that is the work of MI5 will be recorded and written up for analysis.
But much of it will just be talk.
There are many considerations; the security of the summit itself, the policing of protests and, away from Fermanagh, what deadly plays the dissidents might engage in. "We clearly have to keep the focus and pressure on the dissidents, while maintaining the highest level of security for the summit itself," Chief Constable Matt Baggott (below) told me.
He knows, of course, that for groups such as Oglaigh na hEireann (ONH) and the dissident IRA this is a chance to be seen and heard.
The presence of world leaders, such as Barack Obama, Vladimir Putin and Angela Merkel, also means the presence of the world's media.
And the story is not just about the summit; is not confined to a couple of days and dates, but entails all the build-up between now and then.
As one example, today Al Jazeera is in Belfast compiling a report on G8 security. No one in the policing/intelligence world is expecting a dissident attack on the summit and any attack on the police cordon would run the risk of injuring protesters.
But ONH and that dissident IRA coalition will know that an attack anywhere and at any time in the next couple of weeks will bring them into the G8 story.
That's why the chief constable speaks of keeping that focus and pressure on these groups.
But he also described this as "business as usual".
"The threat level has been severe for a significant time," he said. And, for his officers, that threat – to use his words – is "day-to-day".
We've seen it in recent attacks in Belfast, in which bogus emergency calls have been made to lure police into gun and bomb ambushes. And, in those incidents, we have also witnessed the finest of lines between life and death.
Two pipe bombs exploded close to officers responding to a call for help in north Belfast last week. "One of those things would take you apart," a source commented – adding that the only thing that saved the officers from serious injury – or worse – was "a lack of accuracy" on the part of those who threw the devices.
And this is that fine margin between what dissidents would term success and failure.
But, as the G8 approaches, the assessment of dissident intentions is but one piece in a much bigger jigsaw.
"This is a high-security event and high-security operation and its planning is meticulous," the chief constable said.
The gathering of world leaders on such a stage also means the possibility of international threats and there will be covert security and all the associated paraphernalia that won't be seen, or discussed.
In terms of preparation and planning, the chief constable said: "We've drawn on all expertise – international and national. The Met experts from the Olympics – they are working alongside us. Colleagues from Canada, who've had a G8."
Add to this more than 3,500 officers from England, Wales and Scotland who will be here as part of "mutual aid" arrangements, as well as the thousands of PSNI officers the chief constable says will be "on it" and you begin to get some idea of the scale of this operation.
It is bigger than anything previously witnessed here. And, in part, this event is meant to be a statement confirming the new Northern Ireland and its new peace.
There are those who will want to spoil that message; make statements of their own that fit with the old 'wars' of this place.
Matt Baggott describes "significant progress" made in interrupting and disturbing many dissident plots. But he is not complacent.
There is no such thing as 100% security or intelligence – and there are always gaps and glitches.
And, for all of the listening that comes with eavesdropping, there will be things that won't be heard. So, for all the meticulous planning, the jigsaw is never complete.
That said, Matt Baggott told me: "We are prepared." And that's all the security and intelligence planners can do: prepare as best they can; hope that nothing comes in under the radar; hope the stage and the message are not spoiled; and hope that, when the curtain comes down on the summit, that security will have done its job.
It is a huge piece of work – and it is both a huge challenge and a huge worry.