Hmm... I grow SCARLET Emperor runner beans. Is that the same as your Red Emperor? Maybe it's a variety that is available in UK but not as much here.
As dried mature beans, I cook mine like kidney beans -- soak, drain, then cook with plenty if water until they are soft enough to poke with knife tip or mush depending on what I am making.
The pods on mine are edible when immature -- before they develop the zipper string and definitely before the hard plastic-like inner membrane develops. I just kept trying at various stages -- my kids preferred the beans to be more mature with more developed beany flavor and less of the green flavor of the pod so it made it tricky to pick at just before they got too stringy/hard.
I cook really immature pods in a little salted boiling water covered until the pods are soft and changes color but not overcooked to the point of mushiness and olive green -- a little longer than green beans. Older pods are cooked down usually in chili like meat and tomato stew. My kids don't like spicy.
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