In 1533 Dermot accompanied O'Brien, King of Thomond, and Ulick na Cane, of Clanricard, to the Court of King Henry VIII, where they surrendered their territories. In return, Henry gave them English titles, as well as Letters Patent for all the possessions they already had, but which, in future, would be held at the pleasure of the British Crown - and subject to forfeiture in case of any confederacy or disturbance against the Crown. Dermot and his heirs thus became Knights of King Henry VIII of England, with a duty to offer 'knight service' to their King, when required. The Letters Patent, dated 3 Dec 1543, carried a list of the O'Shaughnessey lands including, "All the manors, lordships, towns and town lands of: Gort, Drommeyell, Dellynellan, Ballyhugh, Monynean, Ardgossam, Ballyegan, Kapparell, Clone, Tollenegan, Laughtyshaughnessy, Cregg, Karrynges, Tirrelagh, Rathwilledoon (Tubber), Ardamullivan, one third part of Droneskenan and Rath, the moiety of Flyngeston, Domlebabehue, Coole and Beagh."

In 1559, Sir Dermot the Lord Deputy when that official was on a 'Martial Tour' of Galway. The meal was sufficiently sumptuous for the Lord Deputy to report to London that the like of it had hitherto not been seen in any Irishman's house. It would appear that hospitality was a traditional virtue of the O'Shaughnessys, probably dating from their ancestor, Guaire, King of Connaught, whose hospitality was celebrated in the folklore of the area.

Sir Dermot O'Sheghyn, Knight, captain of his nation, had a grant from King Henry VIII, which was later interpreted as making him owner of the whole territory of his clan, although in most cases the chief was granted only the demesne lands attached to his office, the rest being divided among those entitled under Brehon law.180

Dermot O'Shaughnessy having accompanied O'Brien King of Thomond, and Ulick na Cane, of Clan-Rickard, to the Court of King Henry VIII, they surrendered their territories; and the Lord Deputy states, that they had no sterling money, as none could be had in the kingdom; but that he lent them some in harp groats; and he says, in a letter addressed to King Henry, speaking of O'Bryan--'That ther repaireth with O'Brien one O'Shaughness, a goodly gentleman dwelling between Thomond and Connaught,' and adds, 'We know no suite he hathe but only to see you and take his lands, and be your subject.' Henry VIII wrote afterwards to the Council in Ireland, stating that he had created 'O'Shaghness' a knight, and directing them to make out a patent for 'o'Shaftness,' and others, of their lands, such as they have now in their possession; and in a note it is stated, that O'Shaughnessy was to have a Bishoprick,' or some other spiritual dignity for his kinsman Malachy Donohoo, and the Bishoprick of Kilomacduagh for his son William Shaftness. On the 3rd of December, 1543, Sir Dermot received his patent from Henry VIII, which recited, that although he and his predecessors, Kings of England, were the true possessors of the lands therein named, yet, that Sir Dermot and his ancestors possessed them unjustly against the Crown until lately: being truly sensible thereof, he relinquished the same, and accordingly granted to Sir Dermot, Chief of his name, and his heirs male in capite, by the service of a knight's fee, all the estate which he had in the manors, lordships, lands, &c, of Gort-Inchegorie, and several other lands, with a proviso, however, of forfeiture, in case of any confederacy or disturbance against the Crown.181