to be brutaly honest its probably just that ie dying . its a fare old age thow it mite be worth livning up the soil around the box and feeding it etc . if this doesnt work i would dig it all up and revitalise the soil and grow something else there maybe . it seams from this picture that the left hand side is suffering the most but it mite just be the angle . i dont suppose theres a tree or large shrub that is taking the goodness from this side of your box is there ?

Dear Nosypotter
will try feeding,thanks for your help

Anniet

maybe feed it and give it a realy nice make over including maybe a nice mulch and a small sculpture or water feacture . its crying out for it and it will help the plant mostly and you will make another piece of your garden a little garden in itself.even a seat mite be nice . sorry i love garden design and ive been thinking about your interesting dilemma . i think you could bring that box back . im not being rude but people get the idea trees and well established shrubs assume they never need feeding againe or watering or nice soil to live in . the thing is the soil gets compacted round something like this or trees and eventualy with all the unnatural traffic the soil gets realy compactded till its nearly waterproof . we are all guilty of this im sure . i hope ive wet your appetite as you have mine lol .

It looks like there used to be something up against it to make that area bald of leaves. A good feed will probably help it to recover from that. Pruning about 1/5 of the stems back into the bald area will also help stimulate new growth there. In the long term, try to gradually rework the shape of the hedge, so it is narrower at the top than at the bottom. That will help keep the bushes full at the bottom.