In 1204 the French king, Philip Augustus completed the conquest of Normandy from King John and set the seal on the break-up of the Anglo-Norman realm created by William the Conqueror. At this moment the French court was clearly emerging as the most admired and powerful in Europe, its protocol and fashions aped everywhere. Amongst these was a spatially complex and structurally daring style of architecture termed Gothic.
The Gothic style transformed English architecture over the 13th century and beyond. Under its influence, the tower on a rectangular plan so favoured in Romanesque castle building passed out of fashion for a century. In its place circular or semi-circular, and more occasionally polygonal, designs reigned supreme. At the same time, regularised castle plans with four towers set at the angles of a quadrangular enclosure became common. Particularly important in the introduction of French architectural forms to English castle design were the royal works to repair the castles of Dover and Windsor that followed serious siege damage in the civil war of 1216-7.
English masons redevelop French Gothic ideas in an idiosyncratic way. Amongst their most celebrated creations in this idiom are the series of castles built by Edward I to secure his conquest of Wales from 1277.