Sainsbury's have announced a "no challenge" policy, and my local has been true to that so far, but in five visits I have only seen one other unmasked person. This when it was 90%+ before July 24th. Obviously people are acquiescing, either for fear of prosecution, or of harassment or simply of drawing attention to themselves. I suggest, in view of police statements indicating a lack of enthusiasm to get involved absent public order offence, that the latter explanations are more likely. I suggest this site should have a page listing numbers of people intending to visit a certain shop within a certain time frame to coax the more timid into helping to reach the tipping point when the whole policy becomes unenforeceable anywhere.