Recommendations for a 9ft high living, thin, hedge near a house
I'm trying to find a plant/hedge/tree that can grow (or be bought) at 9ft tall, but be thin, but isn't a danger near a house.
Basically, an existing (about to fall down) 6ft fence isn't tall enough to stop us overlooking our neighbours shower room when we are in our ground floor kitchen, as we're on a hill above them, and there is a 3ft step in the land (and a retaining wall) and a 4ft difference on top of that.
I'm needing something "thin" (1ft) to keep access paths open.
I was thinking a living willow hedge, but being close to drains worries me, and not sure about planting willow hedge in a sunken trough.
Are there any other recommendations? It's in heavy clay soil, running north south, in full sun.
(Building a new fence greater than 6 ft means planning permission, which I don't want to go through)