With the erection of Maesyfed into the shire of Radnor in 1536 Rhayader was named as assize-town for the newly formed county in conjunction with New Radnor; but in 1542, on account of a local riot, the town was deprived of this privilege in favour of Presteign.
Rhayader constituted one of the group of boroughs comprising the Radnor parliamentary district until the Redistribution Act of 1885.
He protests in favour of Lord Monteagle's motion for inquiry into the sliding scale of corn duties; of Lord Normanby's motion on the queen's speech in 1843, for inquiry into the state of Ireland (then wholly under military occupation); of Lord Radnor's bill to define the constitutional powers of the home secretary, when Sir James Graham opened Mazzini's letters.
Wyatt; the Guildhall; the barracks, which are the headquarters of two battalions of the South Wales Borderers; the county infirmary founded in 1832; and the prison (in Llanfaes) for the counties of Brecon and Radnor.
A chancery and exchequer for the counties of Brecknock and Radnor were also established at Brecon Castle, and from 1542 till 1830 the great sessions, and since then the assizes, and at all times the quarter sessions for the county, have been held at Brecon.