Hi, this usually grows on rotting wood, so I think something has happened to your plant, that has already killed it, I think I would check all the plants in the hedge, to see if there are any signs of damage or dead parts, and remove any that you find, Derek.

Thank you Derek, that is the plan, we're going to have a serious look at all of it and keep a good eye on it. There is a lot of fresh growth on the hedge so it is not all doom and gloom but I don't like the look of this stuff at all, so it will have to go!

Isn't this what's also known as Jews Ear, or used to be? (sorry its not very PC) I get it on my self sown elder occasionally but not in such a large amount! Have also seen it on wild elder in the woodlands. Didn't know it was a danger signal so thank you both of you for raising the alert..

It does seem to have lots of names, Wikipedia says it is mostly on Elder, but it also says it grows on both dead and living wood. It also says it is edible, whereas another site says it is poisonous. I wouldn't have thought anyone would want to eat such a gross looking thing. We think it may be the vast amount of rain we've had. Other years we have had many 'weird looking' mushrooms in the garden (near our dead old tree dstump) but they looked like proper mushrooms and simply die back down into the ground. Funny thing is we haven't seen those at all this year.