Information on Hillforts
There is a lot of information available on hillforts, here’s a start:
General introductions
Brown, I. 2009. Beacons in the landscape. The hillforts of England and Wales. Oxford: Wingather Press.
Forde-Johnston, J. 1976. Hill Forts of the Iron Age in England and Wales: A Survey of the Surface Evidence. Liverpool: Liverpool University Press.
Harding, D. 2012. Iron Age hillforts in Britain and beyond. Oxford: Oxford University Press.
Hogg, A.H.A. 1975. Hill-forts of Britain. London: Hart-Davis MacGibbon
Ralston, I. 2006. Celtic fortifications. Stroud: Tempus.
Web-based resources, notably Google Earth, can also be helpful.
National sources
England
If the site is a Scheduled Ancient Monument (and many hillforts are) a plan should be available from The National Heritage List for England: https://list.english-heritage.org.uk/advancedsearch.aspx. Use the Advanced Search facility to search by district and parish, where this is known; or search for individual hillforts and enclosures by site name.
The Royal Commission (now English Heritage) has various publications, ranging from County Inventories to for example regional studies such as Exmoor, Dartmoor, the Malverns, and the Quantocks, which include hillfort plans. Also some EH research volumes, such as Northumberland Hillforts, and the Wessex Hillforts Project https://www.english-heritage.org.uk/publications/wessex-hillforts-project/
There is also a large number of unpublished hillfort surveys in the National Monuments Record, (or ‘EH Archive’ as it is now called), including the original Ordnance Survey ‘antiquity models’. Information on these can be accessed from the EH Swindon centre:
Your local county/unitary authority Historic Environment Record (HER) will also probably have information including a plan. For a list of these, see https://www.heritagegateway.org.uk/Gateway/CHR/
Wales
Cadw (www.cadw.wales.gov.uk) holds records on protected monuments.
Cadw, the Royal Commission on the Ancient and Historical Monuments of Wales (RCAHMW), the National Museum Wales and the four Welsh Archaeological Trusts (Gwynedd, Clwyd-Powys, Dyfed and Glamorgan-Gwent) all provide information for an online resource called the ‘Historic Wales Portal’. The portal provides an overview of the records held by each organisation and can be found at: www.historicwales.gov.uk
The Royal Commission on the Ancient and Historic Monuments of Wales (www.rcahmw.gov.uk) curates the National Monuments Record of Wales (NMRW), where there is an index to the drawings, manuscripts and photographs held in the NMRW archive collections, see www.coflein.gov.uk
Each of the four Welsh Archaeological Trusts holds a Historic Environment Record (HER). These are a principal online source of hillfort plans and information on sites, but tend to be variable from one area to another, see www.archwilio.org.uk
The Trusts have also undertaken major surveys of Small Enclosures in their areas, including hillforts, and details and copies can be found on-line at each of the Trusts’ websites as follows:
Gwynedd – www.heneb.co.uk
Clwyd-Powys – www.cpat.org.uk
Dyfed – www.dyfedarchaeology.org.uk
Glamorgan-Gwent – www.ggat.org.uk
The Royal Commission Inventories contain plans and information and can be found at the various Record Offices and Libraries of each of the Welsh Unitary Authorities. Ask for the ‘Inventory of Ancient Monuments of the Royal Commission’ for the county with which you are concerned, also asking for the Volume that concerns the Iron Age and hillforts. They are also available online https://www.rcahmw.gov.uk/HI/ENG/Publications/Bookshop/Inventories/
Most local authorities in Wales have an archaeological service and sometimes details of the important hillfort sites can be found on the website of the individual council concerned.
The most important journal publication pertaining to prehistoric Wales is Archaeologia Cambrensis, published by the Cambrian Archaeological Association, but the transactions of the various county and regional societies of the area of your interest can be useful. Consult your local County Library Service.
Scotland
The principal sources of plans for forts in Scotland are the OS 25-inch maps and the County Inventories prepared by the Royal Commission on the Ancient and Historical Monuments of Scotland (RCAHMS).
The latter are available through many libraries and can be consulted in the reading room of RCAHMS, John Sinclair House, Bernard Terrace, Edinburgh EH8 9NX. The catalogue of original drawings held in the National Collection is available online through CANMORE at https://www.rcahms.gov.uk. Relatively few of these drawings are yet digitised, but original ink drawings and pencil surveys dating from 1913 and after can be consulted by appointment. The original ink versions of many of the forts surveyed for the OS 1:2500 map are included in the archive set of OS index cards in the National Collection and can also be inspected on request.
The Proceedings of the Society of Antiquaries of Scotland is the main source for plans drawn up prior to the establishment of the Royal Commission in 1908 and are available online via the publications section of the Society of Antiquaries of Scotland website at www.socantscot.org
Plans may also be available through Local Authority Sites and Monuments Records/Historic Environment Records (HERs), see https://www.archaeologyscotland.org.uk/index.php?q=node/214
Plans appearing on the 1st and 2nd editions of the OS 1:10560 maps are available online from the National Library of Scotland at https://maps.nls.uk, where they can be inspected in a seamless zoomable format covering the whole of Scotland; 1:2500 sheets are available as individual sheets. For the zoomable format, a National Grid Reference copied from Canmore can be inserted to take the user directly to the site concerned.
Northern Ireland and Republic of Ireland
A listing of known hillforts in the Republic of Ireland is available in Archaeological Survey of Ireland see: https://www.archaeology.ie/
Location and other data for recorded archaeological monuments in the Republic of Ireland is available at https://webgis.archaeology.ie/NationalMonuments/FlexViewer/
A similar listing of hillforts is also contained in the Northern Ireland Sites and Monuments Record see: https://www.doeni.gov.uk/niea/other-index/content-databases/content-databases-ambit.htm
The Republic of Ireland surveys list hillforts, hilltop enclosures and promontory forts, with location and summary site descriptions available for many examples. If information for the monument has been digitised, a brief description of the hillfort is accessible, although site plans are not available. Other information may be available in the County Archaeological Inventory publications for Ireland. This web-GIS also provides various background layers which can be toggled on/off. These include historic Ordnance Survey mapping (1st and 2nd editions and 6-inch and 25-inch scale), vertical aerial photography and Discovery series mapping. A similar digital archive of aerial photography and OS maps are available at Ordnance Survey Ireland’s website (https://maps.osi.ie/publicviewer/).
There are a number of site specific publications which contain detailed plans of some hillforts, for example the Discovery Programme’s ‘Western Stone Forts Project’, ‘North Munster Project’ and ‘Ballyhoura Hills Project’ publications (see https://www.discoveryprogramme.ie/research/). Other publications that contain hillfort plans include Professor John Waddell’s The Prehistoric Archaeology of Ireland, (Dublin Wordwell 2000 2 edn) and Professor Barry Raftery’s Pagan Celtic Ireland (London: Thames & Hudson 1994).