Batch building and site-specific design

Edward's works are unusual because the Crown ordered related groups of castles within supporting distance rather than commissioning isolated sites years apart. Their designs do not form a simple evolutionary sequence ending at Beaumaris. Master James and Edward fitted each castle to its site, mission, budget, and construction time. Flint concentrated defense around a central tower into which a small garrison could retreat while still controlling the enclosure and retaining an escape route. Island-bound Beaumaris used a moat, outer wall, inner wall, and successive obstacles to consume an attacker's lives and time before the defenders faced a final crisis.