Proc Soc Antiq Scot, (1995)5 12 , 499-519 Westerton: a Roman watchtower on the Gask frontier W S Hanson* & J G P Friellf ABSTRACT The excavation of the Roman timber watchtower at Westerton was undertaken to obtain dating evidence and a complete plan. The four-post tower was more elongated in plan than anticipated provided frontwas the at and with steps giving accessfirst-floorthe to level,a feature readilynot paralleled excavatedin towers anywhere Romanthe in Empire.one The fragment f probableo mortarium recovered frome singleth enclosing ditch s commensuratei with a Flavian date. Disturbance of the post-holes indicated that the tower had been deliberately demolished. The tower consideredis relationin otherto adjacent examples which Gask makethe up frontier. The function of this system is discussed and placed in its broader historical context. INTRODUCTION existence Th seriea f eo f timbe o s r towers alon Gase gth k Ridg lons eha g been known beste Th . - preserved examples follow the line of the Roman road to the east of the fort at Strageath along this low ridge of hills, which runs approximately east/west immediately to the north of the river Earn. e numbeTh f siteo r s know s grownha n ove pase , largelyear0 th rso 5 t r o sy through aerial reconnaissance resulta s A . , somattested w tower7 1 eno e e distributiosar th , f whicno h extends beyon Gase dth k Ridg enorth-easte botth o ht , towarde th o fore t t Berth Taye sth a d t th an , n ao south, past the fort at Ardoch (illus 1). The term 'Gask frontier' has now come to be applied to this more extended system, even though only part of it follows the Gask Ridge itself (Breeze 1982, 72). This terminolog hers yi e preferred becaus t maintainei slina k wit best-knowe hth n elemene th f o t system. The alternative descriptor, the Tay/Forth frontier (Maxwell 1990, 355), has implications which, though likely, have yet to be proven. Several of the towers were investigated by Christison (1901) around the turn of the century otherd an , s ove las e year5 th r2 t Robertsoy sb n t Josep(1974S d han ) (1973, 218; 1977, 136-9). Despite the considerable attention that has been paid to the Gask frontier, there remain major difficulties in placing the system in its correct historical context because of the lack of direct dating evidence onle Th y. dateable artefact recovere above th df e o froexcavationy man s has been one piece of pottery, a fragment of Flavian mortarium from Gask House (Robertson 1974, 20-1). In addition, presumably because it was assumed that they were very simple structures, none of the more recent excavations made any attempt to obtain a complete plan. It * Department of Archaeology, University of Glasgow, Glasgow G12 8QQ t English Heritage, 23 Savile Row, London W1X 1AB 500 SOCIETY OF ANTIQUARIES OF SCOTLAND, 1995 HANSO FRIELLN& : WESTERTON ROMAA : N WATCHTOWE CASE TH KN FRONTIERO R 501 ILLU S2 Westertoe Roma th line f th eo n d roanan r d(Crown ai fro e mth copyright: Royal Commission on the Ancient and Historical Monuments of Scotland) was in an attempt to address these deficiencies that the excavations reported here were undertaken. site t Westertoea Th 87291458N n(N discoveres )wa cropmara s a dr ai fro ke m th (illuy b ) s2 St Joseph (1951, 62), and is the most northerly of the towers known in the stretch of Roman road fore soute t Strageathth a th t f ho o t nort e ridgw th t standlo hn I . e o a sid n thaf so eo t road witn ha unobstructed view over Strathearn to the north and to Kaims Castle fortlet on higher ground 2 km southe th o t . Sinc ploughes site t epreviouslth ewa no d dha flatt y bu ,bee n examined t offerei , n a d ideal opportunity to obtain a complete plan with the minimum of damage to the surviving archaeological remainss thuwa s d expectean , alloo dt e optimuwth m selectio f depositno r fo s removal in search of dating evidence. Permission to excavate was granted by the factor, Mr P G Farquhar, on behalf of Drummond Castle Estates; by the tenant of Westerton Farm, Mr Miller; and by Historic Buildings and Monuments, Scottish Development Department (now Historic Scotland). Fundin provides gwa y db e Universitth f e Glasgoo excavatioyth d an w n took place over three weekendn i s October/November 1979 with the aid of students from the Department of Archaeology. To all these bodies and individuals the authors are most grateful. Since the site was located on top of a natural ridge and was regularly under the plough, it seemed unlikely that there would be anything of value to be gained by excavation undertaken entirely by hand. Accordingly an area of some 500 sq m was stripped of its topsoil by machine surface Th the.s enwa carefully cleane hany db defino dt archaeologicae eth l remains. After the excavation of selected features the site was backfilled and returned to cultivation. All primary records from the excavation have been deposited in the National Monuments Recor Scotlandf do single th d Hunteriae an ,finth n di n Museum, Universit Glasgowf yo . 502 SOCIET ANTIQUARIEF YO SCOTLANDF SO , 1995 THE ENCLOSURE (ILLUS 3 & 4) aeriae th s l A photographs indicated site th e, consiste single-ditchea f do d penannular enclosure 14 internamn i l diameter entrancn A . e causeway 1. wide2m , face Romae dth n road approximate th , e line of which was defined by its quarry ditches immediately to the south-east. The butt-ends of the ditch seemed the most likely places for the deposition of rubbish and thus for the recovery of artefacts. Accordingly two sections were removed on each side of the entrance. A fifth section was excavated on the north side of the enclosure wher ditce eth h appeare wideste b o dt tota .A ditc f emptieds o l lengthm wa 9 f ho . AAC AAA ABB 25 Feet I 10 Metres ILLUS 3 Westerton: site plan HANSON & FRIELL: WESTERTON: A ROMAN WATCHTOWER ON THE CASK FRONTIER j 503 As defined on the surface, the ditch varied in width from 1.5 m to 2.8 m, the edges following a slightly irregular line presumably because of the way in which the cornbrash subsoil had fractured excavatee Th . d sections were more consistend an , m widthn i 5 t 2. d , betweean m 9 1. n were 0.6-1.0 m deep (illus 5, A-C). The ditch profile was of typical 'punic' type, a characteristic noted als t Roundlaoa w (Robertson 1974, 24), wit gentlha y sloping inne rsharpla sidd t ean ycu outer face. In some sections, notably on the north side of the entrance (AAA, AAB, AAC), a slot wid som0.15m d 3 ean e 0. m deep so-callee th , d ankle-breake cleaninr ro g channel provides wa , t da the bottom of the ditch. The ditch filling was broadly consistent in all the sections opened. Primary silt filled the bottom and sometimes continued in a thin layer a little way up the inner face. Above that tended to layea e f dirtb o r y grave llarge w witfe ha r stones representing material whic collapsed hha n di from the steeper outer side of the ditch. The upper fill consisted of homogeneous orange-brown clay-silt admixed with stones, some quite large, presumably the result of later infilling by the plough. The one fragment of pottery recovered came from low down in this upper fill in section entranceAAAe norte th th f ho o t , . There wer signo en f deliberatso e backfillin ditche th f g,o with possible th e exceptio f somno e larger stonebotto e channee a th th t d a sf m o an section i l C nAA large stone in a similar position in the western butt-end section (ABA). There were no direct traces of an internal turf bank or rampart, such as those detected at Moss Side (Christison 1901, 29-30), Parkneuk Gasd an ,k House (Robertson 1974, 18-23) (illu, s6) though give presene nth longstandind an t g agricultural regim e sitth e t thiea s unsurprisingi s . Indeed, on cleaning the interior, plough-marks were clearly visible cutting into the subsoil. However, fragments of turf were detected on the inner side of the ditch in one section (illus 5, B), as they wer t Roundlaa e w (Robertson 1974, 26). Although this might represen moro n t e than material whic falled hha fro n ni originae mth l ground surface presence th , turf eo t thi a f s particular point (section AAA) would be entirely consistent with slippage from the corner of the internal bank of a square enclosure. At both of the sites where internal banks have been recorded by modern excavation (Parkneu Gasd kan k House) enclosuree th , s they defined prove square b o dt e rather than circular in plan, following the outline of the tower rather than mirroring the inner scarp of the ditch. INTERNAL FEATURES (ILLU) 4 & S3 All four post-pits visible aeriath n leo photograph (illu ) wer2 s e located t witbu , h surprising difficulty. They were carefully define removiny db centimetrew fe ga theif so o r tw fillt onl e bu ,y th facin entrance gth e were excavated regulatheis pitd e th ha swa r f l .shapen o i al rOnl e t yon bu , longer dimension on the same NW/SE axis.