I know another forum member had issues with his well established privet hedge a couple of years ago. He's spent a lot of time removing it.
From what I can remember - it was diseased in some way, and once it starts spreading, it keeps going. In the same way box blight can be hard to stop once it takes hold.
Gareths photo dated 14th of June is suffering from honey fungus identified by the black under the bark, having lost a 60 feet of a 65 year old privet it is devastating the first sign is the spring leaves stop growing new leaves remain small but are retained finally drooping as the plant is chocked usually after a dry spell
you will need to remove all the dead plants with the root and inspect it you will probably find what looks like a black root this is the honey fungus root and how it got in. if this is the case remove all the dead plants as well as the healthy plant and all surrounding earth either side of the affected area although this does not always work I eventually lost the hole hedge. I removed all the dirt and sifted through the soil to remove all traces of the black root, digging down 2 feet placed in some damp proof course with holes in the bottom for water drainage but to deep for the fungus to grow this should prevent the new hedge from any remaining fungus roots in the soil which may work its way back to the new hedge. my new hedge is now 2 years old and almost 6 foot high remember a good even privet should have any stems longer than 6 to 8 leaves long trimmed to get a healthy thick even hedge all over
Have maintained for almost 30 years now approx 200yds/meters of privet/ escalonia/ fuschia boundary hedge near the coast.Hedge planted inside stone boundary wall and could been 70 -75 years old.
To control depth/height/shape has over the years required,on occasions,major pruning with good recovery.
This summer first ever signs of leaf curl and and blackness.After recent west coast storms privet is wilted and black.Escallonia not as bad, but worst I have seen following recent storm. On Anglesey we have experienced worse storms.
Considering trimming and hoping we avoid winter frosts.I am fearing the worst for the privet and possibly other garden hedges, trees and shrubs.?