1. Flint flakes, burnt stones and fragments of hand-made pottery of Iron Age type were found in `ancient dwellings' on Grassholm before 1951. The first modern archaeological survey on the island was carried out by D.B. Hague, then of the RCAHMW, in 1972. Hague initially visited the island in 1963 with the naturalist R.M. Lockley, who had observed during a visit in 1956 that structures were being revealed by the caustic effect of seabird guano, which was killing the dense mattress of Festuca rubra on the western side of the island and exposing the light soil beneath. The visit was brief and only a rough plan of the settlement was made, but Hague returned to the island in 1972 and, during a five day stay, was able to survey and carefully excavate the exposed remains.
Hague's settlement was comprised of three conjoined structures. In the centre was a rectangular shaped house, 9.5 metres by 8 metres, constructed of mixed orthostats and coursed masonry, and standing c. 0.3 metres high. This was abutted to the south by a slightly larger building, 9.5 metres by 11.5 metres, and to the north by a rounded enclosure, 13 metres in diameter. Field walls were traced radiating out from this cluster of buildings to the north and east.
New aerial photography by the RCAHMW in 2001 and 2011, has revealed even more structures on the island. Nestled between rock outcrops on the eastern side of the island are the remains of walls and rectangular structures, covered by tussocky grass. In the lee of a rock outcrop in the centre of the island is a circular building that is likely to be a roundhouse. The prehistoric pottery and roundhouse shows potential for very early settlement on the island, but equally tantalising is the possibility that the main rectangular structures date from Viking, or Early Christian times. The island seems to have been used as a target for bombing practice by the United States Air Force during the Second World War, leaving bomb craters and fragments.
O Davis, RCAHMW, 30 January 2012
2. The island has been visited for the purposes of archaeological fieldwork and reconnaissance on 13/10/2012 and 14/10/2016 in the company of the RSPB.
T. Driver & L. Barker, RCAHMW, 17/10/2016
3. Grassholm is a study site within the EU-funded CHERISH Project 2017-2021.
New LiDAR survey of Grassholm Island. In February 2017, Bluesky, a company specialising in the acquisition of aerial survey data, was commissioned by the CHERISH Project to collect 0.25m ?leaves-off? (winter conditions with low vegetation and bare trees) LiDAR (airborne laser scanning) data of six Welsh islands at low tide. This included a new survey of Grassholm, allowing its archaeology to be analysed and mapped to a high degree of accuracy. Bluesky flew from its East Midlands base and collected the data using its Teledyne Optech Galaxy LiDAR system on 24 February. The processed data is archived with the Royal Commission (Driver and Hunt 2018).
CHERISH Project aerial survey for the Royal Commission on 5th February 2018 included detailed photography of gannet nests across the island for the RSPB to help with monitoring plastic debris in the nests (image refs: CHE 5 Feb 2018 070-130).
4. Trial excavation 2019
On the 21st-22nd October 2019, CHERISH Project staff from the Royal Commission and Aberystwyth University successfully undertook two days of fieldwork, survey and evaluation excavation on Grassholm Island with the permission of the RSPB and NRW. Royal Commission staff had previously made two visits in modern times, in 2012 and 2016, both being day visits lasting only a few hours accompanying RSPB staff on their annual autumn trips to free fledgling gannets from plastic debris (Davis 2012; Davis and Barker 2012). The two-day visit in October 2019 allowed considerably more time for site reconnaissance, survey and record enhancement than had been possible on previous visits; all 5 of the Fieldwork Objectives listed in the WSI (see below) were achieved.
The main achievement was the excavation of a small (2.55 x 0.8m) evaluation trench across House 1 (NPRN 418264) to investigate the character and survival of the building and attempt to reach a floor level for the recovery of datable material. In practice the trench was excavated 0.34m down inside the building and 0.23m outside before the water table was reached. However, probing suggests a possible internal floor level at 0.65m below the modern land surface. As the wall stones protrude only 0.14m above the modern surface the excavation appears to confirm that the standing archaeology of Grassholm is being actively buried by the nest-building activities of the gannets. More detail is provided below.
Overall the previously very wet conditions during much of October, with bouts of intense rainfall, had rendered the archaeology highly visible in the central zone of bare earth and nests. The low walls of field boundaries and structures stood out well against the dark, damp island soil making them easy to see and photograph. In many places disconnected sections of drystone walling or structural orthostats were also noted for the first time, suggesting a deeper history of structures across the central plateau of Grassholm which had probably been built, dismantled or re-used over centuries or millennia.
T. Driver for the CHERISH Team 2019
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