When I first moved into this house 20 years ago there was a fence between our drive and next door’s. Then my neighbour took the fence down when he had the drive paved. Now he tells me he’s going to build a wall. Do we have to agree on this, or can he build it without my permission?
If your neighbour is planning to build the wall along the boundary it will be what’s known as a “party fence wall” and ideally he should give you notification (and the opportunity to object) under the Party Wall etc Act 1996. He probably won’t do this but rather than head down the route of expensive litigation, I suggest that instead you co-operate, and ensure (for example) that the pillars supporting the wall protrude into his drive, not yours.