In May, over the course of two days, a hard-working group of volunteers under the direction of Surrey Archaeological Society undertook an electrical resistance survey across the front and west lawns of West Horsley Place, adjacent to the house. This was done with an aim of trying to uncover evidence of potential features related to the house’s earlier phases of occupation, including former wall foundations and garden walls and paths that have since been buried.

The survey was done at a high resolution of 0.5m by 0.5m, which resulted in excellent clarity of the features and the most detailed geophysical survey to date of the property. Electrical resistance is a technique which measures the pattern differences as electrical current is passed through the ground between twin probes, as buried features with varying moisture content – e.g. ditches and pits versus brick or stone walls – may stand out compared to the surrounding soil. The equipment, an RM Frobisher TAR-3 Resistance Meter, was walked along transects which are spaced half a metre apart, and every half-metre along, the two probes were inserted into the ground, to obtain a reading of the current (in ohms) which passed between the probes at that spot. A map of the readings is then created, which makes apparent some of the sub-surface archaeology. Although it can vary depending on geology, the features detected may be up to 0.75m in depth.

The resulting map, illustrated here in greyscale, depicts the areas of higher resistance (shown in white) versus low resistance (black). The high resistance features are not always archaeologically significant, but it is very likely that former garden walls (possibly flint-built), brick-built culverts, foundations for building walls and garden paths are all represented by some of the white (or light grey) linears seen in the survey. How old they are is not always easy to ascertain, although they can sometimes be interpreted based on using the historic maps – how strong the readings are (i.e. how thick or white the line is) can also help indicate their age by how shallow or deep the features are.

The survey supplements nicely what we know already from the community excavations under Surrey County Archaeological Unit which took place in September 2022, which exposed features including former garden walls across the frontage of the house which are apparent on the 1735 estate map, a brick-built soakaway and culvert and foundations of what was likely a predecessor to the current building. The house’s west wing, which has been dendro-dated to the early 15th century by the Surrey Domestic Building Research Group, would have originally protruded further south than its current layout. Its foundations also show up nicely in the recent survey, although precisely what phases of the house are represented requires more research. Whilst it’s possible that the east wing also originally extended further south, the current gravel drive and turning circle make resistivity survey difficult in this area, as the probes cannot penetrate the ground to detect possible features underneath.

The lawn west of the house, known as the ‘champagne lawn’, is also interesting, not having previously been surveyed or had prior fieldwork to give insight into the survey results. No indications of a former garden on this lawn are provided from historic maps, with the exception of the First Edition Ordnance Survey map of 1871, which depicts a series of garden paths which were in existence by the later 19th century. The geophysics indicates possible circular garden beds which presumably pre-date 1871– and are possibly earlier than the 1735 estate map – especially given the lack of garden features (or anything other than a plain lawn) on this spot in later 20th century aerial imagery.

The team of volunteers who undertook the survey worked well, with few having done resistivity before, and the two teams created, each using one of the Society’s Frobisher machines, covered both lawns as separate surveys which took place simultaneously. The results speak for themselves, and many thanks are given to the volunteers for such excellent work and of course to Surrey Archaeological Society for making the survey possible!