Baffling Bolingbroke: understanding Henry IV’s home

In rural Lincolnshire, nearly 30 miles east of Lincoln, stand the remains of a castle once held by royalty. The remaining walls and towers of Bolingbroke Castle are still 3m tall in some parts, and you can make out its distinctive hexagonal shape. The buildings that once crowded together inside the castle have long-since disappeared.

Bolingbroke Castle was founded in the 1220s by Ranulf de Blundeville, Earl of Chester and Lincoln and through marriage it ended up in the ownership of the House of Lancaster. John of Gaunt, Duke of Lancaster, lived here in the 1360s and the castle gave its name to his son Henry Bolingbroke, later crowned King Henry IV, who was born here in 1367. The history of the site is reasonably well documented, especially compared to castles not owned by the Crown, but there remain unanswered questions about its origins and development.

In 2018 we gave Heritage Lincolnshire a grant to delve deeper. They would carry out a geophysical survey to establish if there are buried remains immediately south of the castle and on Dewy Hill, which might be the site of an earlier castle, built before the stone one still visible at Bolingbroke.

Aerial photo of a green field surrounded by houses. At one end of the field stand the remains of a hexagonal castle.
Bolingbroke Castle on the left and the rectangular ‘Rout Yard’ on the right. Courtesy of Heritage Lincolnshire.

The plan was to use ‘magnetometry’. It works by measuring how magnetic the soil is and then plotting the results on a map. It allows you cover a large area quickly, and over the course of two days the Heritage Lincolnshire team surveyed more than five hectares (about five times the size of Trafalgar Square).

There is some natural variation in the soil, but typically human activity such as cooking hearths or stone walls have a different magnetic signature to the soil around them as they are made from different materials. Magnetometry can also be used to find filled-in ditches as the fill might contain traces of human occupation.

The first stage was to survey Dewy Hill, sitting 400m north-west of Bolingbroke Castle. It was excavated in the 1960s, and a digital survey of the terrain suggests a rectangular feature still survives. We hoped the geophysical survey would show how extensive the buried remains are, and the shape and size might give us an idea of what it is. Essentially, was it a castle or some other type of important place? There was a slight hitch…

But Heritage Lincolnshire did eventually get to take their magnetic gradiometer for a spin! Next, they surveyed the area south of the castle as it might contain an extension of the castle which has since been dismantled. Are there traces of this possible enclosure, or was there perhaps a garden here? In the later Middle Ages it was especially popular to shape the landscape around a castle. Right in the middle of this area is a rectangular piece of ground called the ‘Rout Yard’, but it’s unclear when it was created so the survey aimed to establish how this area relates to the castle.

Understanding the results takes a trained eye, and Heritage Lincolnshire have a highly skilled team of experts. They were able to find a few anomalies, but they either appear to be modern (there may be a concrete slab on Dewy Hill) or natural geological features.

The point of an exploratory project is to find out what lies beneath. Oddly, we expected something to be at Dewy Hill since earlier excavations suggested there might be some activity. The search for a possible bailey suggests that perhaps one did not exist or if it did it may have been insubstantial. That would mean the ruins we see today may represent the extent of the castle at its peak. Interestingly the fashion for having gardens might have passed Bolingbroke by. It was an important place, so may have begun to fall out of use by the time gardens became a common part of high-status medieval landscapes.

Despite the siege of 1643, the survey did not uncover ‘siegeworks’ which would have been built by the Parliamentarians. This might be because the siege was relatively short.

As a result of this work, we know more about how the surroundings of Bolingbroke Castle. Other types of geophysical survey may pick up different pieces of evidence, helping build a fuller picture of the area. Surveys like this are an important tool to understand sites, and Heritage Lincolnshire’s work will inform any future work at the castle.

Thank you to the owners, the Duchy of Lancaster, for allowing us to carry out the survey, to English Heritage who are guardians of the site, and to the volunteers from the local community who helped with the fieldwork. Projects like this really do take a village.

A full report has been prepared by Heritage Lincolnshire.

Going in search of Keith Marischal

In the later Middle Ages, the Keith family were some of the most important people in Scotland. Sir Robert Keith was made marischal of Scotland in 1293, a title that descended through his heirs. As marishal, Sir Robert and his successors were could hold courts during wartime and were responsible for maintaining order within the Scottish parliament. The castle at Keith Marischal, half a day’s journey from Edinburgh, was the family’s ancestral home.

For a family which was amongst Scotland’s richest in the 16th century, their seat was an important place which would have embodied their power and prestige. The great hall, the social heart of the castle, vied with royal palaces in its size. William Keith, 7th Earl Marischal was forced to sell Keith Marishcal during the Civil Wars, and, despite being an important piece of Scottish history, the castle was gradually demolished. Part of the castle survives and was incorporated into the later house built on the site, but much of Keith Marischal has vanished.

Stirling Castle’s great hall. Photo by ‘DeFacto’, licensed CC-BY-SA 4.0.

In 2017, Miles Kerr-Peterson suggested carrying out a geophysical survey to look for buried remains just north of where the house currently stands. He successfully applied to the Castle Studies Trust for funding, and in May 2018 he and Rose Geophysical Consultants visited Keith Marischal to search for the evidence in an area of 2 hectares.

Two methods were used: resistivity and ground penetrating radar (GPR). As different materials conduct electricity differently, testing the electrical resistance of the ground can be used to find features such as walls (high resistance as there is little water) or ditches (low resistance as ditches tend to hold water), and is effective to a depth of about 0.75m. GPR works by sending electromagnetic pulses into the ground and tracking how they are reflected. Part of the area north of the house is a carpark, which makes survey resistivity ineffective, but GPR can still be used.

Deciphering a geophysical survey takes a trained eye. The resistivity survey found several features, and working out what they are has been an interesting challenge. There are two features running in a mostly straight line perpendicular to the current house at the west end of the survey. The longer of the pair could be a drain, but it’s uncertain. And what are the features at the north end? The feature runs beyond the edge of the survey, so we don’t know the full shape and size of it. With trees nearby it could even be part of a root system, but the straight lines suggest it could be man-made and could be part of the lost castle.

GPR allows us to peer deeper, and to work out a rough stratigraphy of features. The survey was able to corroborate some of the anomalies found with resistivity. The pair of parallel features at the west end are visible, but the one on the right runs deeper. The fact it’s so narrow suggests it might be a drain. The GPR also found an anomaly at the north end of the survey area, lining up with the one found using resistivity. It was visible some 0.38-0.63m deep, which suggests it might be artificial rather than natural.

The results of the survey are certainly interesting. We didn’t find the extent of the lost Keith Marischal Castle, but most discoveries don’t happen overnight. Geophysics is an excellent way to identify areas of interest ahead of excavation. Without excavation, we can’t be sure about the interpretation of these features. If the anomaly at the north end of the survey is part of the lost castle, we don’t have a way of dating it without breaking out a trowel.

The survey was a vital step in the understanding Keith Marischal. Thanks to Miles and Rose Geophysical Consulting, any future excavations will know where to look. Keith Marischal has an exciting future, and the Castle Studies Trust are proud to be able to have played our part in supporting the work.

Dr Miles Kerr-Peterson is an affiliate in Scottish History at the University of Glasgow. His new book, A Protestant Lord in James VI’s Scotland George Keith, Fifth Earl Marischal, touches on the Keiths and is out now.

The art of the reconstruction

When walking round ruined castles, it can be difficult to picture how they once were. There may be missing floors, the roofs aren’t the same, and entire buildings might have vanished. Even when a structure appears to survive intact, we are usually missing the interior – how it was decorated, the furniture, even how light changed throughout the day.

Reconstructions are a wonderful tool for bringing castles back to life. This year, the Castle Studies Trust is funding one such reconstruction. Chris Jones-Jenkins is helping us understand how Ruthin Castle would have looked. You might recognise his name from 2015, when he worked on one of our very first projects, the digital model of Holt Castle, or from his various work with Cadw and English Heritage.

We caught up with Chris to learn a bit about what goes into these illustrations and how he got into reconstructions. Older illustrations, like those done by Alan Sorrell decades ago, were done by hand while a lot of reconstructions today are done on a computer. Chris has experience of both, and they are very different processes. When working by hand, you need to start off by choosing your viewpoint and deciding what it is you’re going to show. With a digital reconstruction, you have the option to change the position of where you’re looking from. Chris reconstructs everything in the image and the viewpoint might be the last thing to be settled. With Holt for example, if that had been reconstructed 20 years ago the viewpoint would have been one of the first things decided – what to show, what to discreetly tuck away, and how to balance highlighting everything you want. Instead, as Chris created the whole thing digitally it was possible to use the model to create a flythrough video.

A plan of Ruthin Castle from Thomas Pennant’s 1781 edition of ‘A Tour of Wales’, from the collection of the National Library of Wales. Image in the public domain.

A wealth of information goes into reconstructions. For Holt and Ruthin, any standing remains are taken into account and modelled, while historical evidence such as paintings or documents are used to fill in the gaps where parts of the structure are missing. Chris trained as an architect and early in his career so has an eye for how buildings are put together, complimenting his skill as an artist and years of experience with historic buildings. Will Davies and Sian Rees have been helping with the research into Ruthin Castle and how it appeared, giving Chris the best information possible to work from. There was a survey of the curtain wall, but done to the wrong scale, which kept the team on their toes.

Working with some kinds of source material you get a feel for how useful and accurate it is. For instance, in the 17th century Randle Holme made some useful plans of Holt Castle in pen and ink. He also created a view of Ruthin Castle, but for some reason his work here wasn’t as reliable. The test is that the parts of the castle that still survive weren’t well illustrated by Holme, so his work needs to be used carefully.

A lot of time and effort goes into reconstructions. It can take over six months from start to finish, with drafting, redrafting, tinkering with details, and pausing to research a particular feature or issue. Over this time, the reconstruction grows from a plain model to a textured, colourful building. Reconstructions have an element of educated guesswork, but attention to detail is important. If you misstep and include something not appropriate for the period there are eagle-eyed heritage lovers who spot this kind of thing! New information is being uncovered about Ruthin, which directly informs Chris’ work. But there are some questions, like the forms of buildings, which are only likely to be answered by excavation.

Chris has been working on reconstructions since the 1980s, and aside from the change in technology has noticed an interesting trend. Previously, there was often emphasis on showing the structure while more recently the organisations commissions reconstructions want to populate these buildings, showing daily life inside.

Talking to Chris, one thing that cropped up is that reconstruction artists don’t often get to hear what the public think about their work which is a real shame as it can make a world of difference to a site. So when going round a historic site, if you see a reconstruction that captures your imagination or helps you understand the place better, pass on that positive feedback.

The image at the top of this page shows the a work-in-progress version of the reconstruction. Subscribe to our quarterly newsletter so you don’t miss news about the finished reconstruction and our other projects.

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

Don’t miss out on more news from our projects. We’ll have regular updates from Pembroke on our social media, and if you haven’t already please subscribe to our quarterly newsletter. We are entirely reliant on donations, so please consider giving to support our work.

The six projects we’re funding this year

From 15 high quality applications we had to choose which ones we could fund. It certainly wasn’t an easy decision, but we have managed to support six different projects – the most we’ve supported in a single year – with a total of £22,000. You can learn more below, and if you would like to hear about the results when they are ready be sure to sign up to our newsletter.

Old Bolingbroke, Lincolnshire, England

Photo by David Hitchborne, licensed CC BY-SA 2.0.

Bolingbroke Castle was built by the Earl of Chester in the 1220s and Henry IV was born here in 1367. It is unclear how the Rout Yard and Dewy Hill were used, so Heritage Lincolnshire will carry out geophysical surveys at the castle to find out more about the site.

Pembroke, Pembrokeshire, Wales

Photo by ‘Jez‘, licensed CC BY-SA-NC-ND 2.0.

Founded in 1093, Pembroke is the oldest castle out of this year’s projects. Rebuilt by William Marshall, one of the most famous knight of his age, the castle was also the birthplace of Henry VII. Neil Ludlow and James Meek’s project will excavate in the outer ward to find out more about a late medieval hall. We also funded a geophysical survey at the castle in 2016.

Dig It!, castles of southern Scotland

With funding from the Castle Studies Trust Dig It! will be producing a series of eight videos exploring castles in southern Scotland, and sharing them with an online audience. By making it easier to access information about these important historic sites through YouTube and Wikipedia the project aims to inspire the next generation of castle enthusiasts!

Keith Marischal, East Lothian, Scotland


The Castle of Keith belonged to the powerful Keith family. The castle has since been demolished, with some parts built into Keith Marischal House which now stands on the site. Miles Kerr-Peterson and and Rose Geophysical Consultants will be carrying out a geophysical survey to search for the castle’s lost tower and great hall.

Laughton-en-le-Morthen, South Yorkshire, England


The castle is undocumented in medieval sources, but the earthworks of the motte-and-bailey castle are impressive: the motte itself is 9m tall. To find out more about Laughton-en-le-Morthen Castle, Duncan Wright will be carrying out a geophysical and aerial survey.

Ruthin, Denbighshire, Wales

Photo by Eirian Evans, licensed under a CC BY-SA 2.0 licence.

First documented in 1277, Ruthin Castle was controlled by Reginald de Grey in 1282. This once great castle is a ruin today and much in need of interpretation. To help with this, Chris Jones-Jenkins will create a digital reconstruction of Ruthin. Chris also worked on the reconstruction of Holt Castle, which was built around the same time some 18 miles to the east.

Stay in touch!

We will have updates from these projects throughout the year. Be sure to subscribe to our newsletter so you don’t miss out.

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Another Bumper Crop of Applications for the Castle Studies Trust to Consider

The deadline for grant applications passed on 15th December. We’re going through the various projects now. Altogether the 15 projects, coming from all parts of Britain, are asking for over £63,000. They cover not only a wide period of history but also a wide range of topics. For a little more detail, here are the applications we’ve received:

  • Caldicot, Wales – a geophysical survey of the scheduled area of Caldicot Castle using magnetometry, resistivity, and Ground Penetrating Radar (GPR)
  • Dig It! 2017 Castles of South Scotland – enhancing public understanding and knowledge of some castles in southern Scotland, their purpose, their history and their relevance, particularly the lesser-known and least visited sites.
  • Dunyvaig, Scotland – co-funding a project to provide better understanding of the landscape context of the castle by conducting detailed topographic and geophysical surveys and carrying out trial trenching to gain key information regarding the preservation and the depth of the buried deposits.
  • Keith Marischal, Scotland – geophysical survey at Keith Marischal House, in search of a lost medieval castle and renaissance palace with a great hall reputed to be second in size to that of Stirling’s.
  • Lathom, England – excavations to find out the true size of Lathom Castle. You may recognised them from 2017’s grants when we funded analysis of masonry recovered from excavations between 1997 and 2009.
  • Laughton-en-le-Mortain, England  comprehensive archaeological investigation of the motte and bailey castle of Laughton-en-le-Morthen, South Yorkshire and its surrounding landscape.
  • Loch Kinord, Castle Island, Scotland – radiocarbon dating an early island castle: Castle Island, Loch Kinord, Aberdeenshire
  • Old Bolingbroke, England – revealing the history of Old Bolingbroke’s Castles: What can researching Bolingbroke Castle’s Route Yard and Dewy Hill tell us about Bolingbroke Castle?
  • Pembroke, Wales – test trenches at one of Wales’ greatest castles to confirm the site of the late medieval structure revealed in the geophysical survey funded by the CST in 2016.
  • Ruthin Denbighshire – co-funding reconstruction drawing of this great Welsh Edwardian fortress. Ruthin was the town where Owain Glyndwr’s rebellion against English rule started.
  • Sheffield, England – record and examine the architectural fragments stored on the site of the castle found in previous excavations.
  • Skipton, England – an archaeological/architectural survey will be produced of the gate structures and flanking round towers of the inner ward of Skipton Castle.
  • Snodhill, England – geophysical survey and excavations to answer some key remaining questions of this important Welsh border fortress re: the castle namely where was the entrance and function of the North Tower.

The applications have been sent to our expert assessors who will go over them. You can see how the assessment process works in one of our earlier blogs.