Ruthin's first gaol is thought to have been located in the Old Court House of the Lordship of Ruthin. This half-timbered building, now the National Westminster Bank, was built about 1404 following Owain Glyndwr's attack on the town which left very few, if any, houses standing.

Baronial, manorial and other courts were held; prisoners being detained in cells below the magnificent beamed court room. Richard Gwyn, a Welsh Catholic martyr, spent the last four years of his life imprisoned in the building before his execution at Wrexham in 1584.

Most executions at Ruthin were carried out on St Peter's Square and part of the timber gibbet can be seen on the north-west wall of the court house. It is thought the last person executed was Charles Meehan, a Jesuit priest, who was hung, drawn and quartered in 1679.

The courthouse where the magistrates met at the Quarter Sessions (the old town hall) stood in the middle of the square. Built in 1663 it was demolished in the 1860s.