Pendennis Castle (Cornish: Penn Dinas, meaning "headland fortification") is an artillery fort constructed by Henry VIII near Falmouth, Cornwall, England between 1540 and 1542.

It formed part of the King's Device programme to protect against invasion from France and the Holy Roman Empire, and defended the Carrick Roads waterway at the mouth of the River Fal.

The original, circular keep and gun platform was expanded at the end of the century to cope with the increasing Spanish threat, with a ring of extensive stone ramparts and bastions built around the older castle.

[2] Pendennis Castle was built as a consequence of international tensions between England, France and the Holy Roman Empire in the final years of the reign of King Henry VIII.

Traditionally the Crown had left coastal defences to the local lords and communities, only taking a modest role in building and maintaining fortifications, and while France and the Empire remained in conflict with one another, maritime raids were common but an actual invasion of England seemed unlikely.

[3] Basic defences, based around simple blockhouses and towers, existed in the south-west and along the Sussex coast, with a few more impressive works in the north of England, but in general the fortifications were very limited in scale.

[8] In response, Henry issued an order, called a "device", in 1539, giving instructions for the "defence of the realm in time of invasion" and the construction of forts along the English coastline.

[10] A small gun tower, called the Little Dennis Blockhouse, was built in 1539 overlooking the entrance, and plans were made to protect the anchorage further with five additional castles.

[11] In the event, only two of these were constructed, Pendennis and St Mawes Castle, positioned on each side of Carrick Roads and able to provide overlapping fire across the water.

[12] John Killigrew, a prominent member of the local Cornish gentry, probably oversaw the construction of Pendennis; it was built on his land and he was appointed as its first captain.

[20] As a result, a defensive earthwork was constructed north-west of the castle to protect it against an attack from the land, and an additional gun battery facing upriver was installed alongside the blockhouse.

[24] The failed attack caused considerable concern inside government and the privy council were informed that the castle was not sufficient to prevent a Spanish landing along the coast.

[26] The military engineer Paul Ivey constructed an Italian-styled ring of earthworks, embrasures, bastions and a stone-revetted ditch around the original Henrician castle between 1597 and 1600, using a team of 400 local workers, costing around £80 a week in wages.

[27][a] In the early 1600s England was at peace and Pendennis was neglected; reportedly the garrison's pay was two years in arrears, forcing them to gather limpets from the shoreline for food.

[30] The growing town of Falmouth was a strategically important part of their supply route to the Continent, while Carrick Roads formed a base for Royalist piracy in the English Channel.

[31] Two Parliamentary colonels, Fortescue and Hammond, directed the bombardment of the castle from the land, while Captain Batten, with a flotilla of ten ships, blockaded it by sea, preventing fresh supplies from arriving.

[32] The garrison's defences were supported with artillery fire from a Royalist warship that was deliberately run aground north of the castle to produce an additional gun platform.

[37] The garrison, led by Colonel Richard Fortescue, mutinied, seized the visiting Parliamentary commissioners and refused to leave the castle until the additional pay was granted to them.

[44] A new volunteer unit of artillery was formed in Falmouth to support the forts around the harbour, many of them carrying out training using Pendennis's guns before then deploying elsewhere across Cornwall.

[50] When new concerns about France emerged, an electrically operated minefield was laid across Carrick Roads in 1885, jointly controlled from Pendennis and St Mawes.

[51] New 6- and 12-pounder (2.7 and 5.4 kg) quick-firing guns, supported by machine-guns for close defence, were assigned to the castle to deal with the emerging threat from enemy torpedo boats.

[59] Extensive work was carried out across the castle in the 1990s to refurbish the fortifications and open new facilities for visitors, accompanied by archaeological surveys and excavations; in the 2000s, the sergeant's mess and the custodian's house were converted into holiday cottages.

[67] Further around the ramparts, the East Bastion also has two emplacements for quick-firing guns, dating from 1902, and underground magazines, which were converted into a battery plotting room in the Second World War.

[69] In the south-east corner of the ramparts is the One-Gun Battery, which originally held a "disappearing gun", designed to pivot back under a steel shield when fired.

[83] Further south, near the waterline, is the Little Dennis Blockhouse, a D-shaped gun position dating from 1539, altered in the 1540s and then adapted to form part of a larger fortification covering the whole of Pendennis Point in the late 16th century.

[85] Just along the shoreline to the north-east is the Crab Quay Battery, a set of defences originating in the 16th century, intended to prevent an amphibious landing on the headland, and modernised extensively in 1902.