Thomastown was possibly a Tudor borough incorporated by a charter granted to Thomas FitzAnthony and preserved on the 1541-2 patent roll of 32 & 33 Henry VIII. There was a further charter of 1 Mary I (1552) and Thomastown was enrolled at the insistence of the inhabitants in a charter of 28 Eliz. I (1591), which granted to the provost and burgesses of Thomastown and their successors the right to be a body corporate consisting of a provost and burgesses. Then there were two Stuart charters, 13 James I (1616) and 5 James II (1690). The corporation consisted of a sovereign and up to 12 burgesses. The sovereign was a Justice of the Peace within the borough and acted as such. By 1783 it was described as 'a venal rotten borough', and in 1790 as:
a close Borough in the strictest sense of the words, its only electors being six Burgesses, constituted by the fiat of Lord Clifden (0013), whose pleasure consequently nominates its representatives. Between these worthy wights and the place of which they are electors, there is not the slightest connexion, Lord Clifden not possessing a single foot of property in the town: the whole of that being vested in Eland Mossom (1501), Esq. in right of his wife. They are the confidential depositaries of his Lordship's power, not the honest dischargers of a constitutional trust. Its fate is similar to that of the Borough of Gowran, both being the property of the same person. Its representatives either accelerate, by their pliant parliamentary votes, the creation of Peers and Archbishops, or the purchase of their stations swells the coffers of the noble Lord who appoints them.225
Very little is known about the borough. In 1713 it was considered 'well secured for government'. Henry Agar (0012) became sovereign of Thomastown in 1744. It was formerly under the control of Sir William Fownes (0812) backed by his allies, the Ponsonbys (1696,1702), but after 1744 Henry and his brother James Agar (0015) united to ensure their dominance of the corporation and by 1760 the Agars were in sole control of the borough.226 The £15,000 compensation for its disfranchisement in 1800 was paid to Henry Welbore Agar, Viscount Clifden (0013).
