I've realised why the runner beans have died. And the lupin. And some of the crocosmia which are next to the lupin. Nothing to do with bugsies and everything to so with the fact that I sprayed them with weed killer instead of bug spray.
Now I feel extremely stupid. Ah well, maybe, if I chop the lupin right back to its roots I can stop the rot, so to speak. And runner beans will grow again. And I have too many crocosmia anyway!
But I am very cross with myself.