The Court of Great Sessions in Wales was the main court for the prosecution of felonies and serious misdemeanours in Wales between the second Laws in Wales Act of 1542 and the court's abolition in 1830. It had the same powers in civil law as the King's Bench in England, (it also had equity jurisdiction) and its criminal jurisdiction was equivalent to the English county assizes.
The Court was established under the 1542 Act which formally incorporated Wales within the English legal system. Of the 13 Welsh counties, 12 - that is, all except the County of Monmouth - formed new court circuits. These were Chester (comprising the counties of Flint, Denbigh and Montgomery); North Wales (Anglesea and the counties of Caernarvon and Merioneth); Brecon (the counties of Brecon, Glamorgan, and Radnor); and Carmarthen (the counties of Kayermarthen, Cardigan, and Pembroke). Monmouthshire was added to the Oxford circuit of the English Assizes. The Sessions met twice a year in each county, administering English law in the English language: of the 217 judges who sat on its benches in its 288 years of existence, only 30 were Welshmen and it is unlikely that more than a handful of the latter - members of the higher gentry - actually spoke Welsh.
According to historian John Davies, the treatment of Monmouthshire in this arrangement was the cause of the "notion" that "the county had been annexed by England" and was no longer part of Wales. The National Library of Wales holds the surviving historical records of the Court of Great Sessions.