David, thank you for your comment, but the question is not whether metal detectorists do some damage, but rather is it is serious damage, and, if s, whether that is outweighed by all the information they have recovered. I have no doubt archaeologists under contract with countries like Greece and Italy will spout the views of their cultural bureaucracies or that there may be some British naysayers, but even archaeologists of great stature like Lord Renfrew have recognized the merits of PAS and the Treasure Act.
As for Mr. Barford's credentials, the issue is whether he is a real archaeologist or not. Perhaps he can post his CV which will show how active he really is in the field. It's my understanding that he works largely as a translator for UNESCO and the like..
Peter, the point is that the degree of damage caused by metal detecting is unclear; some British archaeologists believe it is enormous while others believe it is limited. All agree that damage is caused; whether that is "outweighed by all the information they have recovered" is a moot point. A great deal of information has also undoubtedly been forever lost. Many archaeologists concur with the CBA view that it is often simply "better to leave the evidence [in the ground] for future generations to investigate with better techniques and with better-informed questions to ask". We've only reached the 21st Century so far; hopefully we have loads of centuries ahead. Apart from situations where land is threatened by immediate development (the danger posed by chemical fertilisers is largely an urban myth), why the frantic rush?
To some extent, the PAS is a pragmatic solution to the problem of metal detecting, a form of "damage limitation". In that respect, it has been moderately successful - a proportion of detectorists are truly responsible and aid archaeology - but it does not erase the fact that the problem exists. Nor does it alleviate the damage done by a large percentage of detectorists who do not bother to use the PAS at all. Only around 10% of metal detectorists who do use the PAS waive their rights to a reward for their finds, a statistic suggesting that many are really in it for financial gain rather than an altruistic contribution to archaeological knowledge.
Spare me the nonsense about "Mr. Barford's credentials". I addressed your odious but transparently absurd attempt at character assassination in my blog post.