including the ROUND TOWER and SQUARE TOWER

Portsmouth was founded by Richard I and, by the outbreak of the Hundred Years' War, it was a thriving town which prompted several attacks by the French. Accordingly the town walls were raised and later augmented with defences for the harbour itself. The Round Tower, Square Tower, Point Battery and King’s Bastion are surviving segments of these fortifications.





Portsmouth Harbour has been a strategically important port for thousands of years. Earlier use was centred around Portchester, where the Romans had a major military base, but by the twelfth century the settlement of Portsmouth had emerged at the mouth of the estuary. The town was formally founded in 1180 by Richard I (the Lionheart) and by the start of the Hundred Years' War in 1337, it was a thriving community. Unfortunately this prompted multiple attacks from the French - first in 1337 and then, as the war turned against the English, further assaults were made in 1369, 1377 and 1380.


Portsmouth Town Defences


Unlike nearby Southampton, also attacked in 1338 and whose mercantile community subsequently funded extensive stone defences, Portsmouth struggled to raise the funds to build town walls. For over forty years after the initial attack, no defences were built and only in 1386 was an earth and timber rampart constructed around the town.


The Round Tower


To mitigate against the comparative weakness of the town's defences, two towers were built at the narrowest point on either side of the harbour's entrance to support a chain barrier. The fortification on the Portsmouth (eastern) side would later evolve into what is now known as the Round Tower. Constructed between 1415 and 1420, it was disconnected from the town's defences on a small peninsula. It was paired with a similar tower at Gosport and a harbour chain slung between them enabled access into the estuary to be controlled (similar arrangements existed at Dartmouth and Fowey). Initially a simple earth and timber bulwark, it was rebuilt in stone in 1495.


The Square Tower


Concurrent with the rebuilding of the Round Tower in 1495, an additional fortification was added to function as a residence for the Governor. Today the structure looks significantly different from its original late fifteenth century appearance as it was refaced in 1827 concealing the original gun ports.

The Round Tower (left) and Square Tower (right) were both built in 1495. The former replaced an earlier earthwork fortification built on the same site.

Tudor Defences


Henry VIII's reign saw increasing tensions with the continent and in 1522 a new gun battery was added south of the Square Tower - this structure would later become the Saluting Platform. The earth and timber ramparts around Portsmouth town were first repaired in the 1520s and then rebuilt entirely in stone between 1541 and 1544. The new defences had artillery towers covering the landward north and east sides whilst an additional square artillery tower covered the Camber. The Round Tower remained in use and was also upgraded with gun ports. Along with Southsea Castle, another Tudor construction dating from 1544, the new defences came close to being tested as the Battle of the Solent was fought against French forces in sight of the town in July 1545.


Henry VIII died in 1547 and his immediate successors - first Edward VI and then Mary I - made no major upgrades in Portsmouth. In 1560 Elizabeth I added Green Bulwark, an angular bastion, on the southern corner of the town's circuit wall and this would later be upgraded into King's Bastion. The Saluting Platform, initially a timber construction, was rebuilt in stone in 1568. These upgrades were all funded by the first state run lottery.


In 1588 Spain declared war on England commencing with the Spanish Armada. Despite its upgraded defences from earlier in the Tudor era, Portsmouth was identified as vulnerable to attack. A grand scheme for new town walls, complete with arrowhead bastions and similar in design to the fortifications at Berwick-upon-Tweed, was devised. The plan was implemented, built in earth for speed, between 1584 and 1586. Both the Saluting Platform and the Square Tower were incorporated into the defensive circuit with the latter converted into a powder store around 1600 (the Governor had moved out in 1580).

In the 1540s, concurrently with the rebuilding of Portsmouth Town Walls, Henry VIII constructed Southsea Castle

The Glory


At the outbreak of the English Civil War in 1642, Portsmouth (including Southsea Castle) was under the control of its Governor, Lord George Goring. In the months preceding the war he had played both Royalist and Parliamentary sides but ultimately declared for the King in August 1642. Parliamentary forces converged on Portsmouth and on 3 September a force under Colonel Richard Norton, a resident of nearby Southwick, captured Southsea Castle. Gosport also fell leaving Portsmouth untenable for the Royalists. Goring surrendered the town allegedly throwing the keys into the harbour.


Sir Bernard de Gomme


During the mid-seventeenth century relations between England and Holland were at a low ebb over attempts by the former to introduce protectionist measures in its mercantile trade. The First Dutch War (1652-4) had been fought and a further conflict was expected. In 1662 Charles II sent his chief Engineer, ironically a Dutchman, to survey the Portsmouth defences. He was Sir Bernard de Gomme and he commenced substantial upgrades in particular installing a series of outworks to provide layered defence. In 1670, perhaps prompted by the devastating Dutch attack on the Medway in 1667, further upgrades were made to the town walls by installing a stone frontage to the Elizabethan earth ramparts and converting some of the Tudor artillery towers into substantial bastions. The defences controlling access to the harbour were also augmented at this time: de Gomme built an eighteen gun 'L' shaped battery adjacent to the Round Tower. Modifications were also made at Gosport with the town there enclosed by its own walls whilst Fort Blockhouse was also built. A smaller fort, James Fort, was constructed within Portsmouth Harbour to act as a final line of defence.


Eighteenth Century


The eighteenth century saw regular conflict between Britain and France culminating in the Napoleonic wars. Between 1730 and 1750 the town ramparts were enhanced by Colonel Desmaretz. Portsea, the peninsula to the north of Portsmouth, also received landward fortifications at this time. The Round Tower was upgraded and heightened and its interior lined with brick to increase its resilience against increasingly powerful artillery and to support heavier guns. The Square Tower was converted into a semaphore station.


Point Battery


Point Battery was built in 1847 modifying an earlier 'L' shaped structure constructed by de Gomme and it also incorporated the Round Tower which was heightened as part of the changes. The new structure consisted of a battery of twenty-four guns with the majority covering the harbour entrance and the remainder in a two storey gallery providing covering fire along the length of the curtain wall. Barracks were added along with a small parade ground and the site was enclosed with a high brick wall. The weaponry fitted to the battery was upgraded on several occasions in the late nineteenth century and in response to the growing threat from fast motor torpedo boats, quick firing guns and electric searchlights were added in 1904. The battery was upgraded for the final time during World War II with close range weaponry to deny access to the harbour to German submarines and E-boats. A harbour boom, not dissimilar to the medieval arrangements, provided an additional barrier to entry.


At the same time as the construction of Point Battery, the Square Tower was also upgraded. In 1838 a new semaphore tower had been built in the dockyard and, along with development of the electronic telegraph, the Admiralty had no need for the site. The Square Tower was returned to the Board of Ordnance who refitted it in 1848 enabling it to take modern heavy guns. Although not connected to Point Battery it augmented the fire-power available and, like the Round Tower, was fitted with electric searchlights and anti-aircraft guns in both World Wars.




The town ramparts were demolished in the latter part of the nineteenth century as they were made militarily redundant by developments in weaponry. Instead, a new chain of defences - the Palmerston forts - were constructed in the surrounding area. However, the coastal defences remained relevant and accordingly the fortifications along the waterfront were retained. When these were decommissioned in 1956, as part of a general realignment towards air power, the waterfront batteries (including the Round and Square Towers) were acquired by Portsmouth City Council who demolished the landward wall and stripped away much of the supporting infrastructure. The site is now a promenade.





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What's There?

Portsmouth defences, including the upper storey and parapet of the Round Tower, are open to the public as part of the (free) waterfront promenade. The Square Tower is used for dedicated events and is not normally accessible although the exterior can be viewed.

Portsmouth Defences. The defences around Portsmouth developed over an extended period. Today the waterfront components are the only significant surviving segments.

Round Tower. The Round Tower was initially built as a timber fortification around 1415 but was upgraded into a stone structure in 1495. It controlled a large chain used to block access into Portsmouth Harbour. A searchlight emplacement can be seen next to the Tower.

Round Tower. The Round Tower was once known as the Ridley's Tower after John Ridley, a Royal administrator of Henry VIII's reign who was responsible for the defences of Portsmouth.

Harbour Chain. The chain originally ran between Round Tower and another installation (now demolished) in Gosport. A few links are on display in Southsea Castle.

Square Tower.  The Square Tower was built in 1495 to serve as a residence for the Governor and to act as an additional guntower. It was refaced in the nineteenth century which has obscured the original gun ports. It is adorned with a bust of Charles I.

Long Curtain Wall and King's Bastion. The town walls were started as earth and timber defences in the fourteenth century but were upgraded in stone during the Tudor era. They were rebuilt on multiple occasions in the subsequent centuries.

Point Battery. Built in 1847 around the earlier Round Tower.

Old Garrison Church.

Fort Blockhouse. A view across the narrow stretch of water that leads into Portsmouth Harbour. Fort Blockhouse, built in the seventeenth century (and extensively modified thereafter), can be seen opposite. The tall white tower on the left of the picture is the Submarine Escape Tank which is used to train Royal Navy submariners.

Getting There

The Portsmouth defences are found in Old Portsmouth. There is pay and display parking directly behind the Round Tower/Point Battery on Broad Street.

Round Tower/Point Battery


50.790522N 1.108793W

Square Tower


50.789366N 1.106478W

King’s Bastion


50.787959N 1.102301W

Old Garrison Church


50.789148N 1.104250W

Landport Gate


50.793549N 1.100949W