Whatever their other differences, the two jurisdictions North and South have at least one feature in common, namely, brown envelopes.
In the Republic, these tend to contain wads of banknotes, but in Northern Ireland they are more likely to hold leaked documents from dissident civil servants.
The prominent unionist, Chris McGimpsey, said the latest brown envelope was given to him yesterday by a British government source who wanted the people of Ulster to know what was going on behind the scenes. The single sheet of paper was promptly handed over to the BBC and UTV and, inevitably, dominated the evening news bulletins.
It was the latest in a lengthy series of leaks attributed to "disloyal loyalists" in the Northern Ireland Office.
The latest leak speaks of "a vigorous exchange" between Mr Mandelson and Mr Cowen over dinner in Dublin last month. In sniffy mandarin tones, the author notes that the Iveagh House Minister called for a removal of crown symbolism in the North, "with all the subtlety and open-mindedness that one would expect from a member of Sinn Fein".
This is a rather inaccurate characterisation of Sinn Fein members who, whatever about being openminded, are frequently so subtle that it is hard to know what precise point they are trying to make.
It is certainly the case that bluntness and directness are the hallmarks of Mr Cowen's political style, although this document's attempt to paint him as a Jolly Green Giant probably says more about the prejudices of the anonymous scribe than it does about the Minister's politics, which are essentially pragmatic in the best Fianna Fail tradition.
The content of the document was far less significant than the fact that someone felt obliged to disclose it at such a sensitive time.
The leak also confirmed the suspicion of mounting apprehension in the unionist camp over what might emerge from this week's deliberations. Mr Trimble's conduct at Downing Street this week seemed to be based on the motto that "short visits make long friends"; the republicans, on the other hand, stayed for several hours of discussions.
Even the least politically sophisticated of unionists would know that Mr Adams was not discussing Antrim's chances in this year's hurling championship.
Non-unionist sources shared the feeling that, while a deal might not actually be cooking, recipes were certainly being exchanged. As usual, Downing Street was talking up the progress made. Dublin was being more downbeat, and Sinn Fein, while not ruling out the prospect of success, voiced its usual scepticism about unionism's good faith.
FOR once, observers were inclined to give marginally greater credibility to the London "spin", but neither version seemed totally believable.
The so-called decommissioning deadline of May 22nd turned out to be something of a distraction. The real negotiations and horse-trading have been taking place this week, and insiders hinted that if the deal wasn't done by today, or very shortly, we could forget about serious progress until the early autumn.
The relationship of the leader of Ulster Unionism to the British Prime Minister has been compared in the past with the balance of forces between the mayor of Cincinnati and the President of the United States.
Mr Blair cannot command Mr Trimble to take a certain course of action, but it is generally advisable for a unionist leader to keep his prime minister "on side".
But what if, as speculation suggests, that prime minister wants to make a leap of faith and expects his unionist friends to take the same political risk?
From day one of this process, unionists have been reluctant participants. There were walk-outs on Good Friday 1998, and even those unionists who remained kept their fingers firmly crossed. It has always been a case of London and Dublin leading the unionist horse to water and hoping it will drink.
On the republican side, there has to be a certain satisfaction that the demand for prior decommissioning has at long last lost all political currency. Instead, the cry has been for a declaration that the "war is over".
This is also dismissed as a non-runner by republican sources. But provided the institutions of government are reinstated, republicans might be prepared to reappoint the IRA interlocutor to the de Chastelain commission and the assurances - still unpublished - which the IRA gave to the general on February 11th could go back on to the table.
As filtered through the general's report of that date, the IRA appeared to be offering to put its weapons "beyond use" under certain unspecified conditions. In the past, Sinn Fein has suggested there might be a role for a third party to verify this procedure, although that notion was accompanied by the usual republican quota of caveats.
Senior British sources have spoken with grudging admiration of Sinn Fein's skill at the negotiating table. Almost in the same breath they have gone on to lament the disparate and dissonant nature of unionism. This appears to be the major problem this week. Republicans are willing to make fairly significant verbal concessions but remain concerned about unionism's ability to reciprocate.
Whatever the final outcome, it has been a good week for the republicans, who at worst look likely to secure a strong undertaking from the two governments on the implementation of the non-institutional aspects of the agreement. Unionists seem likely to end up with little more than token gestures on the Patten report.
Should Mr Blair take the ultimate political risk of naming a day for the reinstatement of the Executive, unionism would face a dilemma - stay away and risk political isolation and obloquy, or sit at the cabinet table on the basis that "Ulster's interests must be defended". Any UUP decision would be taken with an eye to the DUP and a keen awareness of the likely consequences in the by-election for the late Clifford Forsythe's Westminster seat and the next election.
On the day that's in it, with the likelihood of bad news from the local council and London mayoralty elections, Mr Blair needs a major distraction. Not for the first time, Ireland could be critical to the longterm destiny of a British government.