William Melton, Archbishop of York, ordered the gaol built to serve Hexhamshire, the Liberty under his ecclesiastical jurisdiction. Work began in 1330 and finished in January 1332. The design is starkly practical: a three-storey rectangular block facing onto Hallgate, built from rubble masonry, with two barrel-vaulted cells in the basement and administrative space on the floors above. The upper levels were originally largely blind, with very few windows; the lancet windows and mullioned openings you see today were inserted later as the building's purpose softened. By the 16th century the gaol also held prisoners from the English Middle March, the borderlands where the cattle-raiding Reivers operated. Inmates were held here on a temporary basis, awaiting trial in the courtroom of the neighbouring Moot Hall.

On 9 March 1761, the Market Place fifty yards from the gaol filled with a crowd protesting changes to the militia laws. Local men were being conscripted to serve, and the rules of selection had been altered in ways that landed the burden on the poor. The North York Militia, called in to restore order, opened fire. About 45 people were killed. The wounded were carried, along with arrested protesters, into the gaol. The North York regiment afterward bore an unwanted nickname that stuck for generations: the Hexham Butchers. The prison itself outlasted the riot by fifty-nine years. Its inmates were transferred to Morpeth Gaol, and Hexham Old Gaol closed in 1820, after 488 years as a working prison.

What does one do with a redundant 14th-century jail? The people of Hexham tried several answers. The building was converted into a bank, then served as a solicitor's office. During the Second World War, its high vantage made it useful as a fire lookout tower watching for Luftwaffe incendiaries. It now operates as a museum run by Museums Northumberland, telling the story of the Border Reivers, the lawless centuries when the gaol was working, and the trade in cattle and ransom that built the violence. The Border Library housed inside holds the Butler Collection, books, recordings and music documenting the culture of the Anglo-Scottish borderlands, assembled by William Butler, a former Chairman of the Northumbria Tourist Board. The building is Grade I listed.

Coordinates 54.971 N, 2.100 W, geohash gcy88. Cruise 2,000 to 3,500 ft AGL for a useful overhead read. The Old Gaol stands a few paces behind the Moot Hall on the eastern side of Hexham marketplace, a small dark rectangular block easy to miss between the marketplace and the abbey. From the air, work outward from Hexham Abbey, which dominates the western end of the marketplace, then track east across the square to the Moot Hall gatehouse. The gaol is the smaller block just behind the Moot Hall. The River Tyne runs to the north, the A69 dual carriageway parallel beyond it, and Hadrian's Wall traces an east-west line about 4 miles north. Newcastle International Airport (EGNT) lies 19 miles east-northeast.