Quantock (Cantok), Thomas of (d. 1309), royal clerk, chancellor of Ireland, and bishop of Emly, was probably born in Bristol, the son of the prominent Bristol citizen and merchant Roger of Quantock. He was one of five or possibly six brothers, of whom only the eldest two (Nicholas and Master John) can be placed in order of birth. The others were Roger (a clerk), Henry, and possibly Richard. The title ‘master’ (which was already being ascribed to him in 1286) indicates that he was a university graduate, most probably of Oxford.
By 1288 Thomas had become a royal clerk and was being sent to Scotland on the king's business, but already by then he seems also to have had some kind of official connection with the Westminster bench, and early in 1290 he was appointed to deputise for John Lovel, the keeper of rolls and writs in the bench, when he went overseas. Early in 1291 he was sent on some kind of official mission to Ireland and in late October of that year was appointed chancellor of Ireland, a position he retained until his death. During his period as chancellor of Ireland, Thomas was a regular visitor to England, perhaps normally in connection with Irish business discussed at sessions of parliament, and in a session of the English parliament in November 1296 he was able to attest that the 1279 statute of mortmain had never been published in Ireland. A number of complaints of misconduct were made against him at the mid-Lent parliament of 1305, including an allegation by Richard de Nugent that he had procured Richard's ejectment from his prebend of Taghmon in the see of Ferns during a vacancy in order to occupy it for himself; but none of these allegations seems to have stuck.
In the summer of 1306 he was elected bishop of Emly in succession to another prominent English clerk, William of Clifford, receiving the temporalities of that see on 3 September. Master Thomas died on 4 February 1309 in Dublin.