By Victor Smith
Featured in the Kent Archaeological Society Magazine, Winter 2022 (open as PDF)
Background and history
Hopefully, this will ensure the excellent condition and continued public visibility of this Scheduled Ancient Monument for years to come.
The fenced western half of this semi-circular structure is exposed at the side of Royal Pier Road in front of Gravesend’s riverside Clarendon Royal Hotel. It is the only blockhouse remaining to view from a network of five which, through the crossfire of their guns, guarded the river approaches to London against a hostile fleet. Moreover, the Thames was a route for a large part of England’s international trade and was, therefore, a vital national asset. The river could also be used as a base for English naval forces. Politically, the blockhouse was, in a sense and however modestly, an icon of a geopolitical rift in the 1530s, characterised by a state of tension between Henry VIII and much of Europe. Indeed, in 1538 an invasion was feared. This resulted in the inception of an ambitious English programme of defence construction at sea and on land, of which the Gravesend Blockhouse was a part. Its design took forward new Continental approaches to defences for mounting gunpowder artillery. Bespoke artillery fortifications had emerged in Renaissance Italy from the 15th century, and designs evolved. In general, though, the form of the new English works probably reflected current north European practice, but with some similarities to earlier Italian examples. The designs adopted by the defence planners in England were portrayed, for example, by the ideas in an earlier treatise by Albrecht Durer (1527). These embraced the use of enclosed gun casemates, often in rounded bastions, as demonstrated in the remains at Gravesend. Such a built form is familiar from the survival of Deal and Walmer Castles, as well as elsewhere at other coastal locations in Britain. Henry VIII is thought to have contributed to design.
Built on the riverbank’s edge, the blockhouse was a robust D-shaped brick tower or bastion. It was arranged with guns to fire onto the Thames from the inside through gun ports on two levels and from an embrasured roof. Additionally, there were guns in external ground-level positions on either flank. The guns, originally twenty-one in total, differed in their types and calibres, whether muzzle or breech-loading and cast in iron or ‘brasse’, as described in the original armament listing. With the addition of a ‘bumbard’, presumably a larger calibre weapon, they varied between 3 and 9 pounders, with a theoretical range of up to a mile. They could cover the river in a crossfire with the Tilbury blockhouse on the north shore, just 800 m. away, and secure a vital ferry crossing between Kent and Essex. In addition to the guns, there were drawn bows, pikes and bills for local protection. The permanent garrison was a commander, a porter, ten soldiers, and gunners, to be reinforced according to need during a war period. The original armament of guns was hardly mighty, and more powerful guns were introduced later, particularly in the external gun positions.
The blockhouse was a deterrent during the Spanish Armada crisis of 1588 and the Dutch Raid on the Thames and Medway in 1667. In the rear of the blockhouse, during 1665, quarters were added for the Duke of York when he was Lord High Admiral (subsequently crowned King James II). This building later became the residence of successive Ordnance Storekeepers. Sometime, perhaps before the end of the 17th century or not long after, the blockhouse was converted into a gunpowder depot magazine, but the external gun positions were retained and rebuilt in several phases. A major remodelling occurred in 1780 when its eastern gun lines were almost connected with New Tavern Fort, built in the same year.
By the 1830s, the blockhouse was judged to be militarily redundant, and, in stages, its grounds were sold off. The blockhouse itself was sold separately. In 1844, with the assistance of the use of explosives, it was demolished down to just below ground level, with the external gun positions having already been levelled. A small extension of the land followed this into the river to provide a leisure space for the clientele of the Clarendon Hotel (not yet called ‘Royal’), into which the storekeeper’s quarters had been converted.
Archaeological excavation in 1975-6 by the Thameside Archaeological Group, with modest subsequent investigation, revealed what can be seen today. There was a fascinating array of discoveries, including masons’ marks, carved masonry and mouldings, ceramics, roundshot and cross-bow bolts, implying the presence of that type of weapon and the earlier-mentioned drawn bows. Tantalisingly, the eastern half of the blockhouse is hidden under the Clarendon Royal Hotel’s riverside car park. Other parts are just to the rear under Royal Pier Road. Remains of stables and a small detached magazine may still exist at the rear of the site.
As a display of lower courses of walls, the blockhouse is reminiscent of other displayed archaeological sites across the country of various types and periods, whether of stone, brick or both. Such exposures have been retained where this has been judged to be to the heritage and educational public benefit. The blockhouse, with its interpretation panel on the path alongside its fence, is emphatically in this category. The wide and lower stone-faced walls date from the original building of the blockhouse and reveal the lines of infilled gun-ports, with iron rings on either side. The internal walls were, perhaps, to support lower parts of the gunpowder magazine from the original conversion of the building or later adaptations.
The heritage value of continuous remains exposure was recognised, and, with the generous funding of the then owner, Berni Inns, the structure was stabilised in 1980, its setting being landscaped. Unfortunately, successor owners allowed the walls to fall into neglect, and 19 years ago, with the support of English Heritage, the exposed remains passed into the ownership of Gravesham Borough Council. At the same time, and after preparatory volunteer effort by Thames Defence Heritage and with funds secured for the purpose from English Heritage and the council, the building was restabilised and its immediate setting re-landscaped.Over time, exposed walls can be affected by the following:
• The dislodging of fabric by the effects of frost
• Invasive growth allowed to erupt from the structure
• The effects of rain and surface water penetration
• Vandalism and anti-social behaviour of intruders
• Poor stabilisation
• Differential temperature between the host structure and repairs
• Falling out of pointing
Some of this had become apparent enough to justify a reference to the council from the author, Peter Torode and the Gravesham Heritage Forum. Remedial work began, ably carried out by Universal Stone of Wickford, Essex, a company with experience in this type of project. As this progressed, imperfections in previous stabilisation became apparent, particularly the inappropriate use of sand and cement instead of lime. The opportunity has been taken to undertake a comprehensive programme of works to more certainly future-proof the remains.
The author’s report to the council of 14th April 2022 commended for the future a regime of documented condition monitoring and attentive spraying of any invasive growth to head off future problems before they become serious. Global warming should help by reducing the incidence of the disruptive effects of frosts. The author has also suggested the renewal of the now rather tired-looking information panel and, when energy costs have returned to an affordable level, the re-establishment of monument lighting to return the blockhouse to being an enhanced visual asset at night. As well as this, re-positioning some temporary structures outside the council ground north of the fenced enclosure might help to re-establish a relationship of the blockhouse with the river.
Most importantly, Gravesham Borough Council has digitally presented the blockhouse as it originally looked through the exciting ‘In Gravesham Footsteps’ initiative. This is a family-friendly augmented reality trail designed to uncover the secrets of Gravesend’s past. The history of Gravesend can be explored by using a smartphone to see some of the town’s historic buildings and heritage sites, such as the blockhouse, which transforms dramatically before your eyes. For more information about this important asset, which locations are covered and how to experience the trail, visit ingraveshamfootsteps.co.uk/map
Earlier excavation revealed what appeared to be large dislodged sections of the front wall. This may suggest that some or much of the debris from the demolition of the blockhouse in 1844 were deposited in front of the building as part of the extension of ground into the river. There might be further brickwork displaying form and shape, stonework such as mouldings and edgings, and artefacts already found internally. The presence of structural material might be tested through geophysics, such as Ground Penetrating Radar. There are also possibilities for archaeologically examining the western gun line, the subject of an earlier preliminary investigation.
A comprehensive history of the blockhouse and the Clarendon Royal Hotel may be found in Victor T.C. Smith and Eric R. Green, The Gravesend Blockhouse, Thames Defence Heritage, 2000. Priced at £2.50, this is available from (a) ‘Visit Gravesend’, Gravesend Borough Market, High Street, Gravesend DA11 OAZ (postal sales enquiries telephone 01474 337600/email firstname.lastname@example.org) or (b) New Tavern Fort and the Milton Chantry Heritage Centre, Milton Place, Gravesend during opening hours (postal sales enquiries 01474 363998/email email@example.com)