With thanks to Maureen and Jim at the Irish Agroforestry Forum.
Makes so much sense Fred.
Thanks Jonny, there's not much that sheep don't tamper with, but they seem to respect an energised electric fence. I have started to prune some of the lower side branches on the alder trees as they are now about 6 feet tall and can hardly believe how easy it is to access the trees. Sometimes simple basic is best.