Diane, I started the same time as you. Within 3 weeks I was so convinced I had a solution that I went to France with friends and stood in front of my sentinelles, convinced the final clue would become apparent I became extremely excited when I found the grave error and the valley opened to reveal the black ships mast, we even dug a hole in the middle of the night in search of the prize! Needless to say I didn’t dig anything up on that trip and although I have found many owls from the comfort of my armchair since, I can’t wait for the COVID pandemic to ease restrictions so that we can travel again. There is no doubt in my mind where I should be stood at the end of the 650, but I am torn on the possibilities for the 520. If anyone is on similar lines to me they will understand when I say my journey to the centre of the earth starts with the 900 clue.