Much is known about life in the Middle East at the time of the Crusades, but one type of vessel still presents something of a mystery.
These ceramic artefacts are called sphero-conical vessels – a term describing their shape – and hundreds have been unearthed across the region.
"There's a range of sphero-conicals, from thin-walled ceramics that could be used for drinking vessels, mercury containers, and all different sorts of stuff," says Professor Matheson.
"But these ones are thick-walled ceramics that we call stoneware. Small containers, small content, withstanding high pressures.
Professor Matheson believes this fourth fragment, or sherd, is from a hand grenade used during the Christian Crusades — the religious wars initiated by Christians intent on reclaiming the Holy Land from Islamic rule.
In naval warfare the Byzantines famously used flame throwers to project a fluid known as "Greek fire", the precise ingredients of which were kept a military secret and remain a mystery to this day.