We planted this walnut tree 33 years ago and it has been cropping really well for 28 years. When we came back from holiday, I noticed the leaves were all turning brown and the nuts turning black and falling off before they mature. During the very wet winter and summer last year, we lost some trees in the nearby hedge line to phytophthora (root rot). I think the walnut has succumbed to this too. I planted a second walnut about 6 years ago, so hopefully this year it will have its first flowers, then some nuts. It is on marginally higher ground, so hopefully it will survive.
Ian