Had this on my wife's Polo. She complained about a squeal after setting off out of the drive. I drove forward, braked and heard the squeal. I then reversed back onto the drive quite quickly and braked. There was a small rattle and the piece of gravel (flattened on one side) was sitting behind the wheel. A small mark was visible on the disc. No more rattle or squeal. The roads near us had just been tar sprayed and spread with tar and gravel!
