Sir William ap Thomas began the current Raglan Castle after buying the manor in 1432. His son, William Herbert, remodeled it on a much grander scale in the 1460s, adding the gatehouse, a Great Tower drawbridge and an apron wall. The hexagonal Great Tower was probably begun in the 1430s or 1440s. The article names no architect. The Somerset family later added a hall, a 126-foot (38 m) Long Gallery and gardens.
The walls use pale Redbrook sandstone, Old Red Sandstone and Bath Stone for detailed features, and the hall roof was Irish oak. The Marquess surrendered on August 19, 1646, after a siege in the First English Civil War. Parliamentary forces slighted the walls.
The Duke of Beaufort owns it, and Cadw administers it. It is Grade I listed.

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