Is there a rule about been overlooked by adjoining property that is on hill??

I visited an elderly couple recently who live in a bungalow and noticed that their next door neighbours were extending their bungalow that is on a hill directly above them. The bungalow is quite old and had only one window, a bedroom, overlooking them, but the new extension looks as if the house has been transformed in that the front door, a corner window and another window will directly overlook them. The situation would be very severe if the neighbours cut back an evergreen hedge. The distance between the two houses is about 50/60 feet. Would the site be visited by a planning person before permission was granted and is there any restriction in such a construction? It just looks odd. I should add they have created a yard as well ie the slope into the garden has been filled in but there is some garden still between boundary.

No rule. However if the extension is subject to planning they are entitled to object. have the elderly couple raised this as a problem themselves? best approach initially would be a discussion with the neighbor as to the effect of the development and some agreement which would best suit both parties!