6.7: Surface Survey According to 'Our Portable Past'

There is an official document that sets out Historic England’s approach to good practice with regard to surface-collected portable antiquities in the context of field archaeology and survey programmes (including the use of metal detectors). These guidelines also serve as a suitable benchmark for the information of land managers and individuals involved in giving consent for archaeological projects whatever the legal status of the site or sites involved. These guidelines therefore can be used to define good practice in the treatment of the archaeological record by responsible artefact hunters. It has to be said, however, that despite three editions, this is a very confused and unbalanced book that results from some very muddled thinking about surface survey.

The text refers in several places to the use of metal detectors, Historic England warns recognises that potentially serious negative impacts can result from "the unstructured collection and recording of material from such sites". They state [p. 5] that any disturbance of a site should be within the context of an overarching framework that:

- minimises destruction;
- maximises knowledge of the site;
- adheres to a structured set of principles.

The document sets out the basis for the structuring of those principles for surface/ modern ploughzone collection projects. It should be subject to the production and prior agreement of a Project Design and should include a commitment of resources for appropriate assessment, analysis and dissemination of the results, as well as analysis and conservation of any material recovered. The project development process is described on page 8. Few guidelines (or even references to literature) are offered on the actual surface survey process [pp. 8-9].

It just says that the resolution of locational data in field-walking, marine artefact survey or metal-detecting programmes must be appropriate to the type of site and the volumes of material anticipated, regardless of whether the material is simply to be mapped and left in place, or whether it is to be recovered and removed. Locational standards must be appropriate to the specific research aims and objectives of each project. The guidelines add that if collection is undertaken this should incorporate the location of material to a minimum accuracy of 10m squares or transects as a defined sample of the area surveyed; however the precise location of individual objects is preferable. Whatever methods are adopted, the sample proportion in relation to the total area should be recorded. Also suitable non-invasive prospection techniques should be incorporated in the proposed project where appropriate to provide complementary information on context, and to inform evolving fieldwork strategies.

After those brief notes, there is much more written on the use of metal detectors as a survey tool. The guidelines state that they should normally only be used on land under arable conditions, and as part of a properly structured field survey project.As part of surface surveys, metal detectors should only be used to recover material from the contemporary ploughzone, and not from undisturbed contexts. The text indicates that the technique should not be used on sites/ find spots under pasture, unless this is part of an excavation, or where there is unequivocal evidence that the area has been subject to arable cultivation in recent years and if the recovery of material is restricted to the former modern ploughzone.

Section 4 expands on this, talking of the appropriate context for metal detecting (on archaeological sites - both those that are as well as those that are not of national importance or otherwise designated). It is argued that survey work on all previously recognised and important archaeological sites should be carried out to the same high standards as for geophysical and metal detecting surveys on protected places. This work should be carried out in consultation with the appropriate Local Authority Archaeologist and local Portable Antiquities Scheme Finds Liaison Officer.

Any invasive investigation on, or removal of material from, these sites should take place within a clear research framework, should be minimally destructive, and should be for the public benefit. [...] In conformity with these principles set out in the paragraph above, metal detecting on designated sites will not normally be permitted, nor funding be provided for projects incorporating metal detecting on non-designated sites, unless: - metal artefacts are otherwise threatened with loss or destruction and no alternative for securing in situ preservation can be archieved, or
- it takes place within the context of properly formulated research-based fieldwork.
- In these cases metal detecting will not be permitted unless:
- finds are reported/published to agreed standards;
- finds are deposited in an accredited museum that meets appropriate standards (subject to the agreement of the landowner and the provisions of The Treasure Act 1996, or in relation to wreck material, the owner);
- metal detecting takes place as a part of a wider survey or fieldwork programme which would normally include desk-based archaeological assessment and structured retrieval of non-metal as well as metal artefacts. In most cases, additional survey should also include the use of remote sensing or other fieldwork techniques.
Whilst Historic England will not seek to restrict the activities of responsible and law-abiding metal detectorists it will not fund, license or recommend permission be given for any metal-detecting survey as part of an archaeological project on designated or undesignated sites unless it meets these requirements.

Appendix 3 [pp. 30-1] is a ' Case Study: Metal detecting on historic battlefields' that gives more information on the techniques to be used in searching a surface site:

Detecting surveys should not go deeper than the modern topsoil, as the exceptional evidence from any stratified remains can only be adequately recovered by excavation. It should also avoid land uncultivated since the action as exceptional evidence here may be very shallow.
Only archaeologically led, systematic detecting surveys should be undertaken on nationally important battle and siege sites, because most of the evidence lies in the variation in density of artefacts across the site. It is not enough to GPS record each find location as part of a ‘random wander’. There needs to be a well-documented consistent survey coverage, because the variation in numbers of finds and even complete gaps in the record must reflect the total numbers of finds in the ground, not how much time was spent in any area. [...] Systematic survey is best achieved by detecting along accurately recorded, evenly spaced transects marked by lines of coloured flags. The detectorist walks only along the lines, thus each time sampling a strip 2-2.5m wide. Surveys should also use experienced detectorists with high specification machines as otherwise recovery rates can vary dramatically, so distorting the recovered pattern. The spacing of transects depends on site type and the purpose of the survey. [...] if the survey is for development-led evaluation or recording before destruction then, whatever the type of site, more intensive detecting is needed to recover a larger sample.

References:
Historic England 2018, 'Our Portable Past: Guidance for Good Practice' (3rd edition, 20 February 2018)

Tamara Kroftova comments:
"How many British artefact hunters have read 'Our Portable Past'?"