One possibility is that you've left them to long, to eat as a green bean pick before the beans start to form in the pods when they're young and tender. Runners tend to get fibrous as they age.

Annette

Could be they got too hot. Subjected to heat, runner beans will form short pods with only a few seeds. The long, straight pods form in cool weather.

Are you talking about Scarlet Runners, Phaseolus coccineus? Or the types of Phaseolus vulgaris sometimes referred to as runner beans?

If the former they need to be harvested and eaten before the beans inside are developed. Almost before they are even discernible, in fact. The pods should be long and flat. With regular rain and temperatures around 60 - 75f we have been chomping our way through runner beans for 5 weeks now and they show no signs of slowing down. We have so many I don't bother with any where the beans are developed. They go straight on the compost heap. I haven't got time to turn them into 'shellies' and I haven't liked them like that when I've tried them.

Unsure what the beans were. I think they may have suffered from too much sun! I will chance the growing area next year. Thanks for your help