Slice or chop the fresh cucumber into bite-size pieces. Pour the canned beans in a sieve or colander and rinse them well. Once drained add the beans to a large mixing bowl and add the cucumber and the chopped red onion.
Slice the piquillo pepper up (or the peppadew pepper or red bell pepper if you are using this instead) and add it to the beans in the mixing bowl.
Chop the arugula finely and add it to the bowl.
Stir well. Then add the black olives and season the salad with a pinch of pepper and salt. Drizzle with the olive oil and the lemon juice.
Stir the bean salad well again and crumble or dice the feta cheese. Add it to the salad, stir and check the seasoning. Add extra pepper, salt, olive oil or lemon juice to taste if necessary. Scoop the salad into a clean bowl and place it on the fridge for another 10 minutes before serving.