My neighbour has recently laid the blockwork for his new patio and it probably about a 1m high at our boundary. It's on sloping ground so probably less than 300mm above the ground at the other end. It's not ideal as they can see in a lot of our garden, but not all. I don't want an argument with them. I plan to have a conversation mentioning privacy and that above 300mm it should have planning, but I won't cause an issue. Does this apply as the ground is so sloped? He could maybe reduce it by a course l, given the height at the other end.