Creating a boundary barrier with no foundations?

Hi,

My neighbour is on higher ground and its their boundary, a retaining wall with a hedge on top. The wall meets our tarmac driveway.

They are seeking permission to work on a hedge tree (a tree that they objected to us working on) and this will create a hole in the boundary.

Any advice on how we could plug the hole without ripping up the tarmac? 

Im wondering if there is some sort of freestanding mesh fence?

They won't let us attach anything to the wall.

Thanks