The first fortification appeared in 1093, when Arnulf of Montgomery drove a stake into the promontory beside the Pembroke River during the Norman invasion of Wales. A century later, Richard I handed the castle and the title of Earl of Pembroke to William Marshal, a man often called the greatest knight who ever lived. Marshal rebuilt Pembroke in stone, raising the massive round keep that still dominates the site. At 23 metres tall with walls up to 6 metres thick at the base, topped by a distinctive domed roof, the keep was a statement of power designed to be seen from every approach by land or water. Marshal's construction turned a timber outpost into the largest privately owned castle in Wales, and his five sons -- each inheriting in turn, each dying childless -- continued to enlarge and strengthen it over the decades that followed.

Beneath the castle lies Wogan Cavern, a natural limestone cave accessible through a passage from the northern hall. In July 2022, archaeologists funded by the Natural History Museum excavated the cave and found something unexpected: bones of woolly mammoth and reindeer, alongside seashells, pig, and deer remains. The evidence suggests that people occupied this cavern during the Paleolithic and Mesolithic periods, thousands of years before any Norman thought to build above it. Pembroke Castle, then, sits on a site that has drawn human habitation since the Ice Age -- a rocky, defensible point above water that made sense to mammoth hunters and medieval warlords alike.

During the English Civil War, Pembroke initially declared for Parliament even as most of South Wales sided with the King. Parliamentarian forces used the castle as a base to capture the Royalist strongholds of Tenby, Haverfordwest, and Carew. But in 1648, at the start of the Second Civil War, Pembroke's commander Colonel John Poyer switched allegiance and led a Royalist uprising. Oliver Cromwell came personally to deal with the betrayal, arriving on 24 May 1648 and besieging the castle for seven gruelling weeks. When Pembroke finally fell, Cromwell ordered it destroyed. The townspeople were encouraged to disassemble the fortress and reuse its stone -- an invitation to erase a symbol of defiance that the town partly accepted. Poyer and his fellow rebel leaders were found guilty of treason.

What survived Cromwell's demolition order proved resilient enough to endure three more centuries of neglect before major restoration in the early twentieth century brought the castle back to something approaching its former presence. The keep stands largely intact, its spiral staircase still connecting four stories of echoing stone chambers. The outer ward retains its twin-towered gatehouse and barbican, and the curtain walls trace the shape of the promontory that made this site so formidable. Pembroke has also found a second life on screen: it doubled as a medieval fortress in the 1968 film The Lion in Winter, starred in Terry Gilliam's Jabberwocky, and appeared in the BBC's Prince Caspian, Shakespeare's Richard II, and the 2016 film Me Before You. The castle that launched the Tudor dynasty now launches movie careers -- a transition that William Marshal, pragmatic to his bones, might have appreciated.