 In 1127 King Henry I granted Rochester Castle to the Archbishop of Canterbury, William de Corbeil, and his successors in perpetuity. He was given permission to build "a fortification or tower within the castle and keep and hold it forever". Corbeil is responsible for building the great tower or keep that still stands today, albeit in an altered state. The 12th century saw many castles in England rebuilt in stone, an advancement in sophistication of design and technology. Although Rochester had already been given a stone curtain wall by Bishop Gundulf, the Keep dates from this period. It visually dominated the rest of the castle, towering above its outer walls, and acted as a residence containing the castle's best accommodation. A sturdy fortification, it could also serve as a stronghold in the event of military action. Such was the importance of the keep as a symbol of Rochester it was depicted on the town's seal in the 13th century.
