The Roman Gask Project (1997)

D.J. Woolliscroft, The Roman Gask Project: A progress report presented to the XVII Congress of Roman Frontier Studies, 1997

The Roman Gask Project was founded in 1995 by the University of Manchester and has since been engaged in an intensive campaign of surveys, excavation and archival work, which has included, where necessary, the preparation of past research for publication. It would be impossible to describe all of this activity in the limited space available, but an overview can be attempted. A fuller description of the project’s aims is available.

Field of study
Firstly, to define the field of study. The Project’s remit has been kept broad to cover Roman Scotland north of the Forth-Clyde Isthmus, but as the name suggests, the principle focus has been on the system of military works on and around the Gask Ridge in Perthshire (fig 1). This consists of a chain of forts, fortlets and towers strung out along the Roman road to the Tay and, on the face of it, there is nothing particularly remarkable about this line. It belongs to a familiar class of early Roman linear defences which also includes the Wetterau Limes in Germany. It is, however, a particularly early example, dating to the 80’s AD.

Indeed, as the German frontier, once thought to be contemporary, has recently been re-dated to the Trajanic period (Kort m forthcoming, the Gask may be the very earliest of these systems: the prototype Limes frontier. As such, it would acquire a special interest to Roman frontier studies, because the state of development of the prototype would have obvious implications for the study of later frontier development. But until recently, although much good work has been done, the system has received relatively little attention. The Project is still at a relatively early stage, but there have already been significant results.

Date of the system
Let us start with the long debated question of the system’s date and length of occupation. The three forts on the line: Ardoch, Strageath and Bertha, show both Flavian and Antonine usage, but it has long been assumed that the whole of the rest of the system must be Flavian. Yet the evidence to support this is negligible. In fact, the entire 37km system of (to date) 21 smaller installations has so far yielded only two published datable finds, and even these are less than helpful. Because one, from Gask House tower (Robertson 1974, 20f), derived from ditch backfill and was thus essentially unstratified, whilst the second, from Westerton tower (Hanson and Friell 1995, 506), came from a similar context and was only tentatively datable as Flavian. Worse still, there has been no dating evidence whatever for the fortlets
. The Project’s own work has done only a little to harden the dating because, although three more datable finds have emerged, all of which were also Flavian, these too came from less than helpful contexts.

Length of occupation
Our work has, however, been of rather more value in shedding light on the system’s likely life span. This is usually assumed to have been exceptionally brief, perhaps only a season or two. For, the Romans did not even get to this area until, at the earliest, Agricola’s third campaign in 79 or 80, whilst Hobley (1989) has argued, from coin evidence, that they must have left again by 86 or 87. But many would doubt whether the system lasted even this long; partly because there has been reluctance to believe that it could have co-existed with the line of so called
“glen blocking” forts further north, and partly because, whilst the forts showed signs of two structural periods, which suggests a need for refurbishment during their life times, the minor installations did not. But here, the Project has modified the picture considerably, because excavations at the two towers of Greenloaning and Shielhill South (Woolliscroft and Hoffmann forthcoming) have found two structural periods in both.

Greenloaning and Sheilhill South
At Greenloaning the evidence took the form of a replacement of the tower’s corner posts at some point during its occupation (fig 2), whilst Shielhill, as well as producing the same post hole sequence, also showed an obvious ditch re-cut (fig 3). Of course
it could be argued that this might indicate that the towers, like the forts, could have been re-used in the Antonine Period but, although Shielhill South did produce one of the new Flavian dates, there have been no Antonine finds of any kind from the minor installations. Moreover, the fact that at both of our towers the replacement posts were set in almost exactly the same positions, would suggest that there was no significant break between the two periods. We would, therefore, appear to have evidence for a more prolonged Flavian occupation because, in addition to the fact that tower uprights 25-30cm thick should not have needed frequent replacement, the ditch re-cut at Shielhill was not dug until a considerable depth of silt had formed in the site’s original ditch bottoms (fig 3).

A similar picture has since emerged at the intervening tower of Blackhill Wood (Pers Comm A. Dunwell of the CFA, who conducted the work LINK). Nevertheless, There remains one problem in extrapolating these results to the rest of the system for these three sites form part of a clear group of four towers at the southernmost end of the system which have two ditches rather than the usual one and there is no guarantee that these sites share exactly the same history as the rest.

Are there then signs of two periods in any of the more northerly sites ? Until recently, the answer was that although there was some evidence, it was impossible to be certain. For example, one of our own excavations (Woolliscroft 1993, 302ff) re-confirmed a fortlet of Midgate, whose existence had come to be denied (Crawford 1949, 54f), despite previous excavation (Christison, 1901, 32ff) and the fact that it remains a conspicuous field monument. (Picture) And it is interesting to note that the site’s ditch comes to within 13m of that of one of the towers.

Obviously then, the two cannot be contemporary, which should offer confirmation of our two periods.

But, ironically, it has recently been pointed out (Hanson and Friell 1995, 514) that whilst the long rejected fortlet is unquestionably genuine, legitimate objections can be levelled at the tower, whose existence had never previously been doubted, for no post holes were found in its interior, albeit in a century old excavation. There is also another difficulty in using evidence from the fortlets because as yet there is no guarantee of their date. We have already seen that the forts have an Antonine Phase and at the moment the only evidence that the fortlets belong with the Flavian tower chain, rather than to the second century occupation, is that Glenbank, at the southern end of the system, has a double ditch like the towers in its area. So they need to be treated with caution.

The Gask Project has, in fact, made two attempts to solve this problem, but both must be counted as failures: firstly at Midgate, whose interior had been largely disturbed and, more recently, at Cuiltburn (Woolliscroft 1997) to the south of Strageath (fig 1). The latter, previously known only as a rectangular air photo target, had been thought to be an entirely new fortlet. But, although the beam slots of an internal building and a fragment of Flavian Samian ware were found, the defences do not seem to parallel those of any other known fortlet.

For it has no internal rampart or palisade, and its ditch has a steep sided, flat bottomed profile quite unlike the normal Roman “V” shape. We seem, in fact, to be dealing with an entirely new site type and, although fascinating in its own right, this brings us no closer to dating the fortlets.

Moss Side
If we restrict our search to the towers, therefore, there are two real possibilities. The first is Moss Side (fig 1). This was excavated in 1900 (Christison 1901, 29f) and, uniquely on the Gask, revealed a set of horizontal beams linking the four corner posts. The obvious explanation is that these would have formed strengthening sill beams and might also have acted as a base for some form of side cladding, perhaps of wattle and daub, to create a usable interior space. This would seem eminently sensible in view of the local climate and the sites exposed position and it is noteworthy that traces of wattle and daub (although not of the beam slots) were found at Shielhill South. But the excavator himself insisted that the corner post holes had been filled in when the beams were installed, so that the posts and beam slots belong to two entirely different periods. The question is: do we believe him, especially given the age of the excavation.

Secondly, there is Westerton. This tower has very elongated post pits, visible even in air photographs, and although only one was fully excavated, it proved to contain two posts like those at Greenloaning and Shielhill South. But, this time, the relationship between them is less clear. The excavators (Hanson and Friell 1995) regarded the two as contemporary and interpreted one as the tower upright and the other as a support for an external staircase and balcony. But the posts’ stratigraphic relationship was never properly established and it does seem more likely that they do represent a similar two period sequence to our own sites.

That was, as stated, the situation until a few months ago and the writer would be the first to admit that, although suggestive, the evidence was far from conclusive. There was only ever one way to obtain a definitive answer and that was to excavate one or more of the northern single ditched towers with this specific question in mind. In July 1998 we, therefore, excavated the northernmost tower currently known on the system: Mains of Huntingtower, on the outskirts of Perth (Links to map and site plan). Had this tower shown only one structural phase we might have been able to claim a slightly different history for the southern double ditched towers, but it did in fact produce two very clear phases with possible indications of a third. That being the case we do, at last, seem likely to have a single unified system with a very much longer occupation that had ever previously been thought possible; lasting probably for the full known Flavian period in northern Scotland, if not longer.

Abandonment of the Gask system
Whatever the duration of the occupation, however, the system was eventually abandoned and there has long been evidence to suggest that this was a matter of deliberate policy rather than the result of at least direct coercion. For we find a general picture of careful demolition and the elimination of useful material. Our own work has added further support to this picture, for Cuiltburn had its sleeper beams dug out, Midgate’s ramparts were partly shovelled into its ditch and both Greenloaning and Shielhill South had their tower posts dug out and burned at the end of the second period. But we can also introduce a subtly different nuance, for although the end when it came may have been orderly, it might also have been sudden and unexpected by the troops on the ground.

Because Midgate seems to have been abandoned part way through a ditch re-cut, not a particularly long job and something that would surely not have been started if the garrison had known that they were shortly to leave.

Building the system
Another area being studied is the building of the system. We have already mentioned the group of double ditched installations at the southern end of the system and this sector has another distinction in that it has fairly regular tower spacings of 3/5 of a Roman mile, whilst the spacings further north are more random (Woolliscroft 1993, 293).

This group might be another hint that we have two construction periods on the system, but there is an alternative explanation. For Hanson and Friell (1995, 513) have recently raised an interesting point which we had also been considering. On, for example, Hadrian’s Wall we have grown used to the idea that differences in design can often represent not different building periods, but different construction teams working simultaneously, and the same may be true on the Gask. If so, can we find evidence for any other such building sectors ? Unlike the Wall, the Gask does not provide the luxury of building inscriptions, but we might be able to tell something from looking at structural differences.

There are a number of criteria that could be chosen. For example the size of the towers themselves, or their shape, for whilst most are rectangular, a few are near perfect squares. But these differences appear to be more or less randomly distributed. The ditches are a rather different story, however, for the known towers appear to fit into four broad groupings. Firstly, again, we have the southern group which, with their double ditches, are not surprisingly the largest sites in overall diameter. Then we have a group of towers from Kirkhill to Midgate towards the eastern end of the Gask Ridge proper, whose single ditches are only 2-3m smaller in diameter than the southern group’s outer ditches and so enclose a great deal more usable internal space. Next, there is an intermediate group from Westerton to Roundlaw which are significantly smaller and finally, we have Huntingtower whose ditch, at less than 17m in overall diameter is barely larger than the southern group’s inner ditch circuits and the smallest site known on the line by a significant margin.

We might argue, therefore, that we have four building sectors and not just two The ditch volumes also follow these divisions. Those of the southern group are puny, often less than 50cm in depth and only just over a meter wide, whilst those of the eastern Ridge group are substantial, up to 1.8m deep and usually 3-4m wide. Meanwhile both the intermediate group and Huntingtower have ditches of around 1m deep and c.2m wide. The intermediate sites also have another distinguishing feature in that, unlike the southern and eastern Ridge groups, the rectangular towers have their long axes parallel, rather than at right angles, to their ditch entrances, whilst Huntingtower is unusual in that the tower is set within the body of the internal rampart, right at the back of the internal area.

All this seems perfectly plausible and coincides well with what one might expect to be the spheres of influence of the three forts and if we do have four groups one can hardly resist mentioning the fact that there were also four legions in the Province at the time, which are the usual builder units, just as there are three milecastle and turret types on Hadrian’s Wall which correspond to the three legions stationed in Britain by then.

There is, however, one small problem. Because Parkneuk, on the western end of the Gask Ridge, which one would expect to belong to the intermediate group, has the widest ditch diameter of any tower on the Ridge proper, and an internal rampart, and a ditch volume in the eastern group range. Its excavator (Robertson 1974, 21ff) thought that its tower was oriented in the intermediate group fashion, but not even this much is certain, and so until more towers can be found in this area, these divisions must be treated with caution.

In a number of other research areas the Project has, as yet, had fewer results.

Length of the system
Firstly, the length of the system. At present the line is only known to run from Glenbank (to the north of Dunblane) to Bertha on the Tay, but there has been much speculation that it might continue both to the north and to the south, through Doune and/or Stirling, towards the line of the later Antonine Wall. Certainly the road is known further south running towards the fort of Camelon (Falkirk), although so far without the accompanying towers, but despite a thorough search of the air photo archives, we have yet to see convincing evidence that it ever ran north of the Tay, despite antiquarian reports and the presence further north of both forts and the legionary fortress of Inchtuthil.

More sites?
Secondly, an intensive search has been made, both on the ground and from the air, for additional sites on the known parts of the line. There is little doubt that these are there to be found, since the spacing pattern still has obvious gaps, but for the moment we again have little to report. Air photography has, however, allowed the course of the road to be plotted with much greater precision and this should help to narrow down the search area for the future.

Discoveries of temporary camps
Thirdly, despite the lack of success in locating new permanent sites, air photographic studies have revealed quite a number of unpublished temporary camps, including a particular concentration between Parkneuk and Ardunie (fig 1). These tend to be smaller than the large, often long known, campaigning camps and may well be construction camps or practice works built during training exercises. These are currently being mapped prior to publication and one small (c. 1.1 acre) camp at Easter Powside, just to the west of Huntingtower, has recently been excavated.

Roman and native on the Gask
Fourthly, archaeologists have long complained that not enough work has been done to study interactions between Roman and native in northern Scotland, and the Project is hoping to make some contribution towards redressing this. We have been mapping the native sites near the system from air photographs and other sources, co-operating with postgraduate work in looking at civilian activity around the forts, and ensuring that organic samples from our excavations will shed light on the ancient environment of the area. We have also conducted two test excavations on the native sites of East Coldoch and Gunnocks, and more such work is planned for the future.

Comparison with other Limes
Finally, a study of the Gask’s signalling arrangements has been made (fig 5), to allow a further comparison with later Limes systems elsewhere. If the Gask really was the prototype Roman frontier, it would be useful to know how developed it was, if we are to judge the level of innovation which look place later, and the signalling system is one indication.

On most of the later Roman frontiers in Europe we see signs of what have become known as Direct Signalling systems, in which almost all of the smaller sites, the fortlets and towers, are carefully sited so as to have a view to a fort (Woolliscroft 1989, 1994 & 1996, plus Woolliscroft and Hoffmann 1991 & 1997). This would have allowed direct signalling via the visual techniques of the day, whilst any remaining sites could have their signals passed on to a fort via (usually single) relays. And, despite its early date, this is also the pattern we find on the Gask (Woolliscroft 1993).

Almost all of the lower lying sites have a direct view to a fort, whilst the fortlet of Kaims Castle has been skilfully positioned to be able to see both Ardoch and Strageath forts simultaneously. Moreover, although the topography of the Gask Ridge itself restricted the views of some of the towers, there is not an installation on the system that would have needed more than one relay to transmit its signals to a fort. This means that apart from the lack of a running barrier we already have on the Gask all of the basic elements of a classic Limes system present in the initial design, sprung, as it were, virtually fully formed from the head of, if not Zeus, then at least the Emperor Domitian and his governor of Britain at the time, either Agricola or his un-named successor.


Crawford, O G S 1949 Topography of Roman Scotland North of the Antonine Wall, Cambridge

Christison, D 1901 ‘Excavations Undertaken by the Society of Antiquaries of Scotland of Earthworks Adjoining the “Roman Road” Between Ardoch and Dupplin Perthshire’, Proc Soc Antiq Scot, 35, (1901), 16-43

Hanson, W S & Friell, J P G 1995, ‘Westerton: a Roman Watchtower on the Gask Frontier’, Proc Soc Antiq Scot, 125, 499-520

Hobley, AS 1989 ‘The Numismatic Evidence for the Post-Agricolan Abandonment of the Roman Frontier in Northern Scotland’, Britannia, 20, (1989), 69-74

Robertson, AS 1974 ‘Roman ‘Signal Stations’ on the Gask Ridge’, Transactions of the Perthshire Society of Natural Science, (Special Issue), (1974), 14-29

Woolliscroft, DJ 1989 ‘Signalling and the Design of Hadrian’s Wall’, Archaeologia Aeliana, 5 ser, 17, (1989), 5-19

Woolliscroft, D J 1993 ‘Signalling and the Design of the Gask Ridge System’, Proc Soc Antiq Scot, 123, 291-314

Woolliscroft, DJ 1994 “Signalling and the Design of the Cumberland Coast”, CW(2), 94, 55-64

Woolliscroft, DJ 1996 “Signalling and the Design of the Antonine Wall” Britannia, 27, 153-178

Woolliscroft, D J 1997, ‘Excavations at Cuiltburn on the Gask Ridge 1995: Interim Report’, Manchester Archaeological Bulletin, 10

Woolliscroft, DJ & Hoffmann, B 1991 ‘Zum Signalsystem und Aufbau des Wetterau-Limes’, Fundberichte aus Baden-Württemberg, 16, (1991), 531-543

Woolliscroft, DJ & Hoffmann, B 1997 “Zum Signalsystem und Aufbau des rätischen Limes.” Germania.

A long term research project to study the Romans north of the Antonine Wall