Posted: 14/09/2015 at 12:34
My Goodness, 30 minutes is way, way too long for runner beans which are fit to eat. You have let them grow for too long. Pick them when they are up to about 160cm and don't need stringing if they are a stringy variety.
One of the joys of your own veg is that you can pick things like beans much earlier than the tough things you find in the shops. And home-grown vegetables, fresh picked, take much less time to cook than recommended.