Although little is otherwise known about his life in Scotland, he was involved in the affairs of Coupar Angus Abbey, while much of his Irish activity coincided with and supported the interests of the Scottish ruling dynasty there in opposing the allies of the MacWilliams.
He left one heir in Patrick, mormaer of Atholl, but the latter's premature death at the hands of the Bisset family meant that Thomas's line had failed by the 1240s.
Thomas was the son of Lochlann mac Uchtraigh [Roland fitz Uhtred] (died 1200), king of the Gall-Gaidhil, and the brother of Alan of Galloway [Ailean].
[3] James Balfour Paul, early 20th-century historian of the nobility of Scotland, remarked that Thomas's activities are very poorly documented in the Scottish records compared with those elsewhere.
[7] Thomas appears to have raped someone at York in this era, an offence for which he received a royal pardon in 1212 at the request of the Scottish king William the Lion.
[9] Tír Eoghain at the time had two rival kin-groups, the Inishowen-based Mac Lochlainn group and the Ó Néill based south of Sperrin Mountains.
[11] Two years later, in 1216, Muireadhach mac Ailein, son of the mormaer of Lennox, defeated and killed the chief of an Inishowen group known as the Cineál Fearghusa, perhaps in support of Thomas's aims.
[8] Thomas's activities against Tír Eoghain may have been related to the attempts of the MacUilleim [MacWilliam] branch of the Scottish dynasty to gain the throne of Scotland.
One of them, Gofraidh mac Domhnaill, had come from Ireland to Ross to renew a bid for the throne in 1211, and Thomas helped oppose him in the resultant royal campaign.
[23] It is possible that Thomas's ability to manage his Irish possessions was hindered by his brother Alan's use of the Galwegian fleet to interfere in Manx succession disputes.