Monument MPM442 - THE ROUND TOWER

Built c1415-1426 as the first permanent fortification in Portsmouth. The tower protected the entrance to Portsmouth harbour as an artillery platform and by operating a chain boom to prevent enemy shipping from entering. Various modifications have been made throughout its history. The remaining upper section dates to the early-19th century, and the inner section contains Tudor stonework.

The Round Tower was built c1418-1426, and was the first permanent fortification in Portsmouth. It was one of two towers that protected the harbour entrance, the second on the Gosport side, between which a chain boom operated. The Gosport tower was a wooden construction, and may have been built slightly later than the Round Tower, although it was considered to be old by Edwards VI's reign. The first documented chain boom was made in 1522, although this may have replaced an earlier one which had been in place when the towers were constructed. Replacement chains were also made in 1664 and 1779, as the metal was corroded by the sea. [1]

During the mid-16th century the tower was known as 'Master Ridley's Tower' after John Ridley who was appointed 'Keeper of the Tower and houses called le Blokehouse (probably the Square Tower) and Berehouse (King's Storehouse)' in 1536. At this date the tower had three gun-ports at ground level and a wooden platform at the top [1]. On the south side was a small projection called 'The Murder House' [2] with ports for small guns or long bows to provide flanking fire across Point Beach. The tower was probably reconstructed during the reign of Elizabeth I, by which time there were six gun-ports, three of which have since been blocked. [1]

The building appears to have been modified for use as a Martello Tower during the early-19th century, when the top was raised and a central column and brick vaulting added to the interior. Stone arches (casements) were also constructed above each of the gun ports inside the tower. In c1850 the tower was raised another 6ft and a bomb-proof expense magazine constructed on top of the north side. [1]

The tower has been modified many times during its history. The remaining upper section dates to the early-19th century, and the inner section contains Tudor stonework. [3]

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The Round Tower fortification. C1415. Ground floor reconstructed c1538-40. 2 upper storeys added probably late C17 by Sir Bernard de Gomme and remodified early C19, possibly for adaptation as a Martello Tower. Top raised and reconstructed and adapted as a gun platform c1850. Restored late C20. Ashlar stone. Roof asphalt paved. 3 storeys separated by stone string bands, lower storey projects. Cylindrical. Entrance facing Board Street has a 2-leaf panel door each leaf with a 6-pane glazed upper panel, set under a cambered stone arch. Facing the harbour on north and west sides are 3 gun ports each set under a flat segmental arch. 3 other gun ports were blocked up probably late C17 by Sir Bernard de Gomme. INTERIOR: rebuilt early C19 was reconstructed and has a large central stone column with brick vaulting, casements formed behind the surviving gun ports. (Balfour A: Portsmouth: London: 1970-: 15; Corney A: Fortifications in Old Portsmouth: Portsmouth City Museums: 1965-: 30, 31 AND 32; Lloyd DW: Buildings of Portsmouth and its Environs: Portsmouth: 1974-: 35,54-56,78,79,102; The Buildings of England: Pevsner N & Lloyd D: Hampshire and the Isle of Wight: Harmondsworth: 1967-: 422).

[4]


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Wessex Archaeology carried out an analytical historic building record of the lower seaward side of the tower in 2025. The recording was divided into three locations: the lower part of the curved elevation (Location 1); retaining wall to the platform now supporting the restaurant terrace (Location 2); late-19th century searchlight emplacement (Location 3). The historic building recording report should be consulted for the full details.

Location 1
Majority dates to the 15th century (c.1415). Some possible 16th century work dating to the reigns of Henry VIII or Elizabeth I. Originally seven gun ports, three remaining. Some ports may have been blocked up by Sir Bernard de Gomme when the defences at Portsmouth were revised between 1662 and 1685. Three remaining gun ports around north side of tower recently glazed and fitted with external bars and some stone in sills replaced. The latter may relate to work carried out in 2012.

Landward side, interior and upper part above lower string course dismantled and rebuilt to increase height and strength of tower c.1815.

Documentary evidence of repair works being carried out in late-1970s but no details could be found or evidence of specific repairs seen.


Location 2
Retaining wall to platform possibly contemporary with early-19th century Flanking Battery. Built from variety of what appear to be reused stones. Partly repointed. Upper two courses reset, possibly in 2016 when restaurant terrace was added.


Location 3
Late-19th century searchlight, now part of restaurant (opened 2016). Original iron shutters removed, window fitted and roof reclad.

Searchlight platform mix of materials and phases. Reinforced concrete core, partially exposed. Facing stones appear to be mix of late-19th century work and 20th century repairs. Set of stone steps constructed between 1998 and 2008, possibly during sea defence work 2003-2005.

See MPM1675 for HER record for the searchlight emplacement.

[5]

<1> Corney, A, 1973, Fortifications in Old Portsmouth - A Guide (Bibliographic reference). SPM388.

<2> Patterson, B.H., 1987, A Military Heritage A History of Portsmouth & Portsea Town Fortifications (Bibliographic reference). SPM43.

<3> Portsmouth City Council, n/a, Portsmouth City SMR Cards (Index). SPM1.

<4> Historic England, The National Heritage List for England (Index). SPM35.

<5> Flood, Grace, 2025, The Round Tower, Broad Street, Portsmouth: Historic Building Recording (Unpublished document). SPM685.