Built on the eastern side of the Carrick Roads, St Mawes Castle has protected the port of Falmouth since Tudor times. Constructed to a geometric plan, the design proved to be a blind alley and new gun batteries were added to compensate during the seventeenth century. The weaponry was regularly upgraded with the site remaining in use for coastal defence until 1956.



In 1534 Henry VIII severed the English church from the established religious order in Rome prompting condemnation from both France and Spain. This was compounded by peace between those two powers potentially giving either the capacity to mount an invasion of England. In 1539 a Device (Act) was issued which initiated the biggest coastal defence programme since the Roman era including the construction of eleven castles and a myriad of other fortifications at vulnerable points along the coast. Falmouth was identified as a weak spot as it had no existing defences whatsoever. Originally something of a back-water, the discovery of America the previous century had seen Falmouth become the first and last safe haven for the growing number of merchant ships braving the stormy Atlantic sea. The entrance into the haven was through the Carrick Roads, a deep and wide channel, overlooked by three headlands at St Mawes, Pendennis and St Anthony Head.


The lack of any defences at Falmouth was seen as a critical shortfall and, as an interim measure, small blockhouses were built at both St Mawes and Pendennis. At the former the structure was a two-storey semi-circular bastion with three gun ports and basic living quarters for a small garrison. The upper level would have been able to support lighter weapons. However, this was only ever intended as a temporary measure and work on St Mawes Castle itself started in April 1540. The castle was geometric in plan and was much closer in design to that of Sandown (Kent) or Walmer castles rather than her sister fortification at Pendennis on the other side of the Carrick Roads suggesting a different team were contracted to build it. The work at St Mawes was overseen by Sir Thomas Treffry, a resident of Fowey, but the builder of Pendennis Castle is unknown. At St Mawes the central tower stood four storeys tall with artillery installed on the top floor and the roof. Below were three round bastions which were each equipped with lower and upper gun floors. A dry ditch surrounded the fortification to provide protection from a land assault. Work completed on the castle around Autumn 1545 with the total cost of construction recorded as £5,018.


The invasion fears of Henry VIII's reign failed to materialise (only one of his castles, Sandown Castle on the Isle of Wight, saw action during his reign). However, during the reign of Elizabeth I relations between England and Spain reached a low ebb fuelled by religious differences and state-sanctioned piracy. St Mawes remained garrisoned through much of Elizabeth's reign and new earthworks were added at the base of the original fort for additional guns. Hostility between the two nations turned into open war in 1588 when Phillip II of Spain sent an Armada against Elizabeth only for it to be defeated by weather and relentless English attacks. In the subsequent years tit-for-tat raids were conducted although the presence of St Mawes and Pendennis meant no direct assaults were made on Falmouth. However, in 1596 the Spanish once again assembled a large fleet ready for an invasion of England and this time specifically planned to attack Falmouth intending to land an army for a protracted campaign. Once again the weather came to the rescue and dispersed the Spanish fleet before they could attack. The death of Elizabeth and accession of James I (VI of Scotland) in 1603 saw peace with Spain. Nevertheless earthwork angled bastions were added in 1623 compensating for the out-dated, circular design of the Tudor castle.


During the Civil War, Cornwall was a Royalist stronghold and both St Mawes and Pendennis were garrisoned for the King. With Parliament in control of the navy both fortifications were key to ensuring that an hostile army wasn't landed in the area which would have threatened exports of Cornish tin that were funding the Royalist war machine. However, by 1646 the Royalist field armies had been defeated and Parliamentary forces were pushing into western Cornwall. Due to the higher ground overlooking St Mawes Castle, it was regarded as undefendable from a land attack and was surrendered without a fight upon the arrival of the Parliamentary army in 1646. The last (mainland) stand was made at Pendennis Castle.


As invasion crises came and went though the eighteenth and nineteenth centuries the armaments at St Mawes were periodically upgraded and the site was garrisoned during both the American Revolution and the Napoleonic wars. By 1780 the sea battery below the castle was equipped with more than 30 heavy guns. However, the peace that followed Napoleon's defeat at the Battle of Waterloo (1815) saw these defences neglected. When the next invasion crisis arose in 1852, the defences at St Mawes were regarded as obsolete. Accordingly the Grand Sea Battery was constructed  consisting of gun emplacements for 10-inch and 8-inch guns as well as a dedicated powder magazine. The old Tudor castle was converted into barracks and modified to make it bomb-proof. The weaponry was upgraded in the 1870s.


The developments in anti-ship weapons continued apace during the late nineteenth and early twentieth century. An electric minefield was installed across the Carrick Roads in 1885 and Quick-Firing guns, intended to deal with a new threat posed from fast motor torpedo boats, were fitted at St Mawes and Pendennis whilst a new battery was built at St Anthony Head between 1895 and 1897. A new four gun battery, located on the hill overlooking St Mawes Castle, was built between 1900 and 1904. Equipped with its own underground magazine it also had an observation post and targeting position.


During World War II, Falmouth was once again deemed vulnerable and Pendennis, St Mawes and St Anthony  were all hastily re-fortified. Whilst long range defence was provided by upgraded batteries at Pendennis and St Anthony, shorter-range twin 6-pounder guns capable of rapid fire to deal with German E-boats and submarines were installed at St Mawes. By 1943 these were radar controlled and ensured the protection of the many vessels being assembled in Falmouth harbour ready for D-Day and the invasion of Normandy. St Mawes, along with other coastal defence sites, was decommissioned in 1956 and thereafter the castle was placed into State care.




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What's There?

St Mawes is one of the best preserved forts built by Henry VIII. Aside from the Tudor castle, the site includes a nineteenth century magazine and gun emplacements. There are also good views of Pendennis and St Anthony Head Battery.

St Mawes Castle Layout. The first fortification on the site was the blockhouse which was built around 1538 and sited at water level to facilitate skimming cannon shot along the surface to hit ships on the waterline.  The Tudor Castle followed in 1540 with the battery to the south of the castle being developed from the 1570s onwards and ultimately becoming the Grand Sea Battery. New Battery was added in 1900.

Tudor Castle. The Tudor Castle was geometric in plan. Whilst the design looks stylish, it was a dead-end in castle development. Within a few years the norm was to build fortifications with straight walls and angled bastions.

Grand Sea Battery. A battery was first installed below the Tudor Castle in the 1570s. Rebuilt on numerous occasions, it was transformed in the 1850s into the Grand Sea Battery which included a dedicated powder magazine.

Getting There

St Mawes Castle is found immediately off the A3078 Upper Castle Road and there is a dedicated car park in the immediately vicinity. In Summer months a ferry runs to/from Falmouth for those wishing to visit Pendennis Castle.

St Mawes Castle


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