Irish Royalty in Rome

A recent post over at the Shrine provoked quite a bit of debate regarding Gaelic Royalty and nobility. Interestingly, there are two sites in Rome with connections to men with claims on the title 'High King of Ireland.'
The better known of these sites is the Church of S.Pietro in Montorio which contains the 'Tombs of the Earls'. The story of the 'Flight of the Earls' is already told elsewhere on the internet - briefly, the Earls of Tyrone (O'Neill) and Tyrconnell (O'Donnell) and their retinues fled Ireland in 1607 following a failed uprising against the British Crown. They ended up in Rome and lived there in exile as pensioners of the Spanish Crown. Had the rebellion been sucessful, O'Neill would have had a strong claim on the throne of Ireland and the title of High King. (It's worth noting that the headship of the Irish Clans and petty kingdoms were not determined by primogeniture, but could be assigned by the clan to any of the deceased man's near male relatives. Nor was the High Kingship an inherited title - its award depended on the relative strenghts and alliances amongst the various smaller Kingdoms and did not necessarily pass to the son of the deceased king.)
The lesser known site of interest is that of San Stephano Rotondo, a fascinating 5th Century round church which seems to have been in a consant state of restoration since the 1950s. In the Battle of Clontarf (1014) the famous High King of Ireland Brian Boru of the Dal gCais dynasty defeated the Leinstermen who rebelled against him and shattered Danish power in the East of Ireland at the expense of his life. His son Donncadh (aka Donatus O'Brien) succeeded to the headship of the clan but was not as effective a ruler as his father. The High Kingship more or less immediately reverted back to the O'Neill Kings of Ulster and the influence of the Dal gCais dynasty declined. Defeated in battle by the King of Leinster in 1058, Donnacadh went on pilgrimage to Rome where he took the monastic habit in S. Stefano and died there in 1064. His tombstone on the left of the church is inaccesible due to restoration works.