But — hey! — some really meaty posting going on here.
A wee bit off-the-main-line, what about a moment's reflection on Richard fitzGilbert, lord of Strigoil, a.k.a. "Strongbow"? Why did Diarmait Mac Murchada approach him in particular?
Oh, and by the way, as I read it, the assumption that Mac Murchada was radically breaching Irish laws of succession goes all the way back to Eoin MacNeill in 1919 (see Studies, 8, pages 367-82 and 640-653). What MacNeill did there was to conflate two very different "legal" prescriptions. The legal "family" was the four-generations of the derbfine — and that, for sure, was the basis of land tenure. So, too, the succession to the kingship was apparently limited to the derbfine. But land is divisible: the office of kingship isn't. Look carefully at the academic debate: G.H.Orpen, whom MacNeill was countering, and — more recently — Donnchadh Ó Corráin, who applied wider anthropology; and the issue is much more debatable — all the way down to Immo Warntjes. In particular Ó Corráin looked at the succession of the Uí Chennselaig dynasty of Leinster; and showed that a fifth of successors did not belong to the derbfine — indeed only 3% of successors could trace themselves back four generations.
A second consideration: in 1126 Toirdelbach Ua Conchobair of Connacht had tried to instal his son, Conchobar, as king of Leinster. Would a blow-in from the West be more acceptable than a Welsh-Norman from over the water?
As for the status of Aífe (and any assumption there was an Irish version of Salic Law), once more I can point to a couple of key articles by Ó Corráin. He looks to the Banshenchas of 1147, which details the parentage and marriages of élite women, and thus underwrites their significance. By the time the Normans put in their appearance, there is ample evidence of women possessing land and disposable wealth in their own rights.
But, back to Strongbow. He wasn't Diarmait Mac Murchada's first resort: that was Henri II himself — but Henri was fully engaged in French affairs, so shrugged his shoulders and let the Norman-Welsh get on with it.
Focus on Richard fitzGilbert, lord of Strigoil, Strongbow. Note that he is not earl of Pembroke, which he had been witnessing the treaty between Stephen and Henri Plantagenet, Duke of Normandy, in 1153. I've just spent some minutes fruitlessly rootling for my copy of Warren on Henry II: he (I recall) lists several earldoms created by Stephen or Matilda which King Henri didn't recognise. Reason: Strongbow had backed Stephen; and Pembroke was kept as a royal fiefdom throughout Henri's kingship (even William Marshal didn't get the earldom when he married Strongbow's daughter, Isabella — he had to wait until he prised it out of King John in 1199) .
Then again there are the fiefdoms of Orbec and Bienfalte, lost to Strongbow's family when they were conferred by Henri, Duke of Normandy, on Robert de Montfort.
In 1164 Strongbow had a strong claim for the lands of Walter, Earl Giffard, who died without male issue. The Giffard lands remained with Henri until his death.
Giraldus Cambrensis' other book on Ireland, the Expugnatio Hibernica, is very telling. When Strongbow made his contract with Diarmait Mac Murchada:
One last teaser: was Strongbow on his uppers? When in 1166-67 Diarmait was recruiting mercenaries one of his contracts was Robert fitz Harding of Bristol. Bristol is on the direct line from Strongbow's HQ at Chepstow — but the city would gain greatly from a Norman presence in Dublin. fitz Harding was a money-lender (and Strongbow appears as a debt on the books of others, including Aaron of Lincoln) , and made a specialism of buying up the estates of others who had backed the wrong horse (i.e. Stephen, now that King Henri fitz Empress was top dog) in the anarchy. Robert fitz Harding's second son had already acquired one of the Strigoil manors.he had a great name, rather than great prospects, ancestral prestige rather than ability: he had succeeded to a name rather than possessions.