By the 1460s, the de Mandevilles abandoned and sold their remaining lands in Twescard to the McQuillans who renamed the territory the Route.
De Lacy in his desire to reclaim all of his earldom, wasted little time in ignoring the terms of his reinstatement and drove the Scots out of northern Antrim, and granted a portion of their land to one of their traditional enemies, John Bisset.
Due to de Lacy's help in conquering the province of Connacht, Henry III indulged his defiance of his reinstatement.
Upon de Lacy's death in 1243, the earldom passed back into the hands of the English Crown, and though it was a troublesome entity, it would prove vital in penetrating deeper into Gaelic Ulster.
The inquisition of 1333 also records the following towns that lay within the land of county Twescard: Le Roo (Limavady), Portkamen (Bushmills), and Portros (Portrush).
The centre of Twescard, Coleraine, recorded as Coulrath, had a fortified bridge, was the forward position for raids into the north-west of Ulster, and vied with Downpatrick to be the second-most important settlement in the earldom after the capital Carrickfergus itself.
By the 1460s, with the earldom of Ulster near its final end, the surviving de Mandevilles of north Antrim, deserted their manors in Twescard and sold their interests to the MacQuillans, who themselves had been driven out of Down.