What should professional archaeologists do about objects discovered by amateurs? The best known cases involve metal-detectorists who, under the English 'Treasure Act (1996), are permitted to make agreements with land-owners to search for antiquities and keep them, although the Portable Antiquities Scheme (PAS; set up to complement the Act's provisions) encourages them to have their finds registered by an archaeologist. There is no doubt that this has greatly increased knowledge of artefacts discovered in England where, in the past decade, the annual number of 'portable antiquities formally reported has risen steeply (Bland 2008: 71). The British Museum is now promoting a code of practice (Bland 2008: 81–2); and, at pains to avoid counterposing professional archaeologists and amateurs, it is encouraging the opportunities for outreach and 'community archaeology' (British Museum n.d.: 16–18). Thus Bland (2008: 80) welcomes collective knowledge . . . founded on public . . . participation' rather than . . . research . . . conceived and executed by professionals'. Yet there are now fresh anxieties about preservation at detectorists' sites (Pestell & Ulmschneider 2003: 9–10; Wilson 2009; Plouviez 2010).