The artillery fort of Henry VIII's King's Device programme

Built between 1539 and 1540, Deal Castle is a stone fortress in Deal, Kent. It was part of a line of coastal defenses commissioned by Henry VIII as part of the King's Device programme. The castle covered 0.85 acres (0.34 ha) and featured sixty-six firing positions for artillery. The Crown spent a total of £27,092 to build the three stone castles of Deal, Sandown, and Walmer, which stood adjacent to one another along the coast and were connected by earthwork defences.

The castle was constructed to protect against invasion from France and the Holy Roman Empire, defending the strategically important Downs anchorage off the English coast. Although the original invasion threat passed, the castle was seized by pro-Royalist insurgents during the Second English Civil War of 1648–49 and was only retaken by Parliamentary forces after several months' fighting.

In the 18th and 19th centuries, Sir John Norris and Lord Carrington adapted the castle to form a more suitable private house for the castle's captain, a position that had become honorary. By 1904, the War Office concluded that the castle no longer had any value as a defensive site or as a barracks and it was opened to the public when the captain was not in residence.

Early in the Second World War, German bombing destroyed the captain's quarters, forcing the then-captain, William Birdwood, to move to Hampton Court Palace. The castle became an observation post for an artillery battery placed along the shoreline. It was not brought back into use as a residence and was restored by the government during the 1950s to form a tourist attraction.

Today, Deal Castle is operated by English Heritage, which received 25,256 visitors in 2008.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons