How did castles such as the White Tower express the authority of medieval rulers?

In the context of Western architecture, castles such as the White Tower served as powerful symbols of authority and essential tools for control during the Middle Ages. Rulers utilized these structures to project dominance and secure their political standing in several key ways:12

• Dominance and Control: Following the Norman Conquest, William I the Conqueror commissioned the White Tower to dominate the local population and control strategic access points, such as the River Thames. These fortifications were built to suppress rebellions and secure the ruler's hold over a newly conquered territory.13
• Administrative and Military Hubs: Castles functioned as bases for administration and military organization. By requiring royal permission to build them, monarchs ensured that these strongholds remained under their direct influence, serving as centers from which they could enforce laws and manage their estates.4
• Architectural Imposingness: The Norman style of castle architecture, characterized by massive, rectangular keeps, conveyed a sense of "massive dignity" and permanence. This imposing design served as a visual reminder of the ruler's power and the strength of the new aristocracy.24
• Last Line of Defense: As the focal point of a castle, the keep was the most carefully fortified area, designed to sustain a long siege and protect the lord’s private apartments, thereby ensuring the survival of the ruling authority even during times of conflict.5