Trial trenching at Pembroke Castle

In 2016, geophysical survey by Neil Ludlow and Dyfed Archaeological Trust (DAT) revealed the remains of long-vanished buildings, and other features, at Pembroke Castle. This work would not have been possible without the Castle Studies Trust, which funded the entire project.

Pembroke is famous for its large round keep, built by earl William Marshal, and a complex of other stone buildings is preserved in the inner ward. But the large, outer ward has been an empty space since at least the eighteenth century. Nevertheless, very dry summers had revealed ‘parchmarks’ here, showing that ruined walls lay just below the surface. These showed up particularly well during 2013 when they were photographed by Toby Driver of the Royal Commission on Ancient and Historical Monuments (Wales), and were published by Toby, with Neil Ludlow, in Archaeology in Wales.

This was the genesis of the current programme of investigation at the castle. The geophysics that followed used a combination of magnetometry, resistivity and Ground Penetrating Radar, to confirm the parchmark evidence and also show that a number of further buildings, and other features, formerly lay in the outer ward. The most exciting of these is a large building which may represent a free-standing, double-winged mansion-house from the late Middle Ages. If so, it would be quite exceptional: grand buildings of this particular kind are unusual in castles, and particularly in outer wards which are normally thought to have contained the more lowly buildings associated with everyday castle life.  It means that the outer ward, at Pembroke, may have been ‘gentrified’ – at least in the fifteenth century. This may make sense of historical accounts which place the birth of the future king Henry VII in the outer ward: it may have occurred within this very building.

What the geophysics and parchmarks seem to show is a large, central hall, flanked by two wings. If the building was anything like others of its kind, one wing will have contained the kitchen and ‘services’ – the buttery and pantry – while the other represented more private accommodation. The outer ward was partly excavated in the 1930s – sadly, without record – but a photograph shows a large, stone-lined pit, apparently leading off the hall, which may be the cess-pit mentioned in an account from the period. A square annexe showed up here in the survey work.

Just inside the castle beside Pembroke’s main gate are parchmarks (where the white tents are). They show the position of a late medieval hall. ©Neil Ludlow

While the results showed what can be achieved through geophysics – and generous grant-aid – their interpretation is, at the moment, still speculation. Only educated guesses can be made about the exact form, date and function of the building. But it has the potential to make a big contribution to the study of castles, and late medieval history, at a national level. So Neil got together with James Meek of DAT to decide how best to get answers to these questions. Only excavation could really provide the answers but, given the sensitivity of the site, which is a Scheduled Ancient Monument, and the importance of the building, minimum intervention, for now, was the preferred approach – a small excavation, primarily just to see how much has survived. This was agreed by Cadw, who granted permission for the hand-excavation of two trial trenches, one across the hall and possible cess-pit, the other across one of the wings. Overburden will be removed, and hopefully the remains of the medieval walls, and any floor-surfaces, will be revealed. It is not intended to go down any further – or at least, not in the present project which will effectively be an evaluation.

We also don’t know how much was removed during the 1930s excavation. While we know there must still be walling, as it shows up in the geophysics and parchmarks, it is possible that the medieval floors may have gone. We hope not, and we also hope that the cess-pit wasn’t emptied, as its deposits could contain valuable information on diet, health, bugs and parasites, while finds that are important to us may have been dumped there as rubbish.

Neil and DAT decided once again to approach the Castle Studies Trust who, very generously, again awarded a grant for the work. This will be supported by help in kind from Pembroke Castle Trust. One of the things also missing at Pembroke is a really accurate measured ground plan, with levels, so for the first time a full topographic survey will also be undertaken. We hope the castle can be persuaded to reveal a few more of its secrets.

Possible layout of the winged building in Pembroke’s outer ward,
based on Cothay Manor, Somerset, and others. ©Neil Ludlow

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Geophysical survey at Pembroke Castle

Aerial photo of Pembroke Castle from the west, showing parchmarks (Crown Copyright RCAHMW, AP_2013_5162)

New work by Neil Ludlow and Dyfed Archaeological Trust (DAT) has revealed the remains of long-vanished buildings, and other features, at Pembroke Castle. Pembroke is famous for its large round keep, built by earl William Marshal, and a number of stone domestic buildings are preserved in the inner ward. But the large, outer ward has been an empty space since at least the eighteenth century.

In 2013, routine aerial photography, by Toby Driver of the Royal Commission on the Ancient and Historical Monuments of Wales (RCAHMW), revealed a number of ‘parchmarks’ in which the outlines of buried walls could be seen, as shorter grass, in the castle. He contacted Neil, who applied to the Castle Studies Trust for a grant to carry out further work at the castle. Thanks to their funding Neil, in partnership with DAT, was able to undertake a full geophysical survey of both the inner and outer wards in May 2016.

Three different methods were applied. Magnetometry, which measures magnetic variation below the ground, was carried out by DAT while Tim Southern undertook resistivity survey, which measures electrical resistance, on DAT’s behalf. Both processes can reveal buried walls and ditches and Ground Penetrating Radar, which can detect features to a depth of over 1.5 metres, was also undertaken in the outer ward, by Tim Fletcher of TF Industries Ltd..

Plans of Pembroke Castle showing the parchmarks and the results of the geophysical survey. Copyright Dyfed Archaeological Trust and TF Industries Ltd.; Crown Copyright RCAHMW.

Survey in the inner ward suggested that two or possibly three previously unknown buildings may lie beneath the grass, but they couldn’t be dated or characterised. At least one of them may, however, be connected with food preparation as neither a kitchen nor bakehouse has yet been conclusively identified at the castle, which would have been necessary to feed the people who made up the earl’s household, his retinue, and the garrison.

The results in the outer ward were outstanding – and surprising. Even allowing for later disturbance, which was slight, the area seems to have been largely empty of buildings during most of the Middle Ages – in contrast to the busy, congested scene that’s normally imagined. This area was enclosed with an impressive curtain wall and towers in the mid-thirteenth century but may always have been envisaged as an open space – for ‘civil’ assembly, for military gatherings, for pageantry and display or for leisure, or perhaps all four; a garden was certainly present by the fifteenth century, and may have been laid out around 1300-20.

Some buildings were however present. A large rectangular building M against the southwest curtain wall, and a possible smaller lean-to N against the southern curtain, are both probably medieval; was the large building for storage, or was it domestic? To account for the apparent absence of a well in the castle, a number of local stories had developed including one which involved a system of water-pipes; the discovery of a possible well, O, may solve the mystery. Most exciting of all was the confirmation that an arrangement of parchmarks G, recorded in 2013, belong to a free-standing, winged mansion-house. Its form suggests that it’s from the late fifteenth century, and it may have been the building within which King Henry VII was born, which is known to have stood in the outer ward.

A ditch formerly separated the outer ward from the inner ward, and a buried masonry structure K, opposite the inner gate, may be a bridge abutment. This ditch was possibly infilled to improve the setting of the fifteenth-century mansion, and garden. Alternatively, the infill may belong to the Civil War period (1642-48) when the castle was held against the Crown, and then against Cromwell. Two former buildings A and B, which overlay the infilled ditch, may date to the Civil War; one of them was associated with a below-ground ‘passage’ that may be a gunpowder magazine. The castle again saw military use during the Second World War, when five ‘Hall-huts’ C were built to house troops based at the castle.

While a number of the other features denote modern service trenches, some may belong to early use of the castle site. A linear feature J may represent the boundary of a burgage plot, perhaps confirming that the outer ward was laid out over part of the town; if so, some of the patchwork of smaller, formless features may also be urban in origin. Others may be hints of prehistoric occupation.

While the results show what can be achieved through geophysics – and generous grant-aid – more work is required before they can be fully understood. In particular, even limited excavation in the mansion may confirm its date and form, and suggest how the outer ward was used during the fifteenth century. The mansion seems to have contained a latrine, so with luck some good palaeoenvironmental evidence has been preserved. Pembroke is a castle of national significance, both architecturally and as a setting for major historic events: it will repay close study.