The "Code of practice for responsible metal detecting", available from the website of the Portable Antiquities Scheme (for England and Wales), suggests:
Wherever possible working on ground that has already been disturbed (such as ploughed land or that which has formerly been ploughed), and only within the depth of ploughing. If detecting takes place on undisturbed pasture, be careful to ensure that no damage is done to the archaeological value of the land, including earthworks.The significance of this clause has been observed by Paul Barford ("Focus on UK Metal Detecting: Straight from the Horse's Mouth").
Yet Suzie Thomas's commentary on this Viking hoard does not comment on the searching of undisturbed pasture, nor on deep searches ("Discovering a Viking hoard: a day in the life of a metal detectorist", The Conversation October 14, 2014). Rather she seems to be happy with the official acceptance of metal-detecting:
today’s more typically co-operative relationship in the UK. The Treasure Trove Unit in Scotland, and the Portable Antiquities Scheme in England and Wales take an approachable stance towards engaging with detectorists.Some of the issues were explored in a forum article (and responses) in UCL's Papers from the Institute of Archaeology [online].
Thomas's paper fails to engage with the nighthawking issue. She cites the 2009 Nighthawking Survey and she suggests that illegal activity was decreasing (a point dismissed at the time by Keith Miller). She does not mention that illegal activity on scheduled sites was actually increasing. Indeed her mention of Norfolk and the acceptance of metal-detecting needs to be read alongside what the Nighthawking Survey revealed for that same county.
It is, perhaps, ironic that the Heritage Lottery Fund and the National Museum of Wales (Amgueddfa Cymru) announced only this week news of a major project to work on material discovered by metal-detectorists ("Unearthing the past: Heritage Lottery grant supports new initiative to get the best from archaeological finds").
Is the continued searching for archaeological material by metal-detectorists in England, Wales and Scotland sustainable?