A large stone ball, believed to have been launched from a powerful medieval catapult during a siege, has been unearthed by archaeologists at Hay Castle.

The ancient ball, which is 29 centimeters wide and weighs 28.5 kilogrammes (4.5 stone), was found during excavations at the castle in Hay-on-Wye.

The “roughly hewn ball” was found 40cm down in the east wing of the medieval mansion, which is currently undergoing major restoration in preparation for when it opens in 2020.

Archaeologists believe the ball was launched from a huge wooden catapult known as a trebuchet, which were first used in Britain in around 1217 among various other medieval siege weapons.

Heavy stone balls, used as the catapult’s ammunition, were deliberately created to be a uniform size and weight so they could be effectively aimed at their target.

Former associate professor of archaeology at Durham University, Dr Chris Cape said: “Trebuchets were not easily created and needed a good engineer to construct them. This means that they usually indicate royal forces, or those of a very wealthy lord.”

The stone found at Hay Castle is believed to have dated back to the 13th century which suggests the castle could have suffered a "well-funded" and "damaging" siege between 700 and 800 years ago.

There are records of various sieges at Hay Castle throughout the 13th century and it is possible that the stone dates from the Barons War of 1263 - 1266.

Similar trebuchet balls were found at Carmarthenshire’s Drylwyn Castle where Dr Caple was lead archaeologist.

Dr Caple said: “The principle of a trebuchet is to catapult a large stone in a sling which is used to release and propel the stone high in the air and into the upper levels of the walls of the building that was under siege.”

Attackers were also known to have fired dead animals, human bodies, excrement and burning items at their targets.

There are modern reconstructions of trebuchets at several castles including Caerphilly Castle and Warwick Castle, which has the largest functioning trebuchet in the world.

You can find out more about the restoration of Hay Castle and how to support the project on the Hay Castle Trust website by clicking here.

You can also follow the project on Facebook and see its progress updates via its Instagram account @haycastletrust.