"bad, very bad, publicity niggles 'em"
That's a debate that continued throughout the campaign. I think it was felt that the reasonable route, if involving a massive enough effort, offered a chance. So, George served up the largest campaign of its type there has ever been in Britain, took the issue directly to an estimated four million people worldwide and delivered to the Council the largest number of objections they had ever received on any subject. Alll of which was cancelled out by a dirty little bureaucratic decision that it applied to the original application but was invalid in respect of the amended one.
With hindsight, the campaign was never going to work then. But as you say, bad publicity targeted right, might have. A couple of billboards on a commuter route into London with the picture of the CEO of Anglo American, saying "This man is stealing a jewel of European and World Culture" would be very rude, the work of ill-informed scallywags, but rather good. The gravel at Thornborough is worth far less than they spend yearly on ensuring they have a positive image.