Runner bean taste

Hi all, I bought a packet of sliced runner beans from Marks and Spencer's one time and they were so tasty that I have been trying to grow every variety I can find to replicate that un explainable moreish taste, with no avail. They all seem to taste the same. I'm thinking it must be what they feed their runners on or their soil that makes them taste so moreish, do you know what I mean ? Thanks

Seriously too many to name them all over the past 3 years, 8 different varieties last year alone. From memory for example I grew firestorm, white lady, polestar, scarlet emperor, Enorma, galaxy and magic among others.
It’s hard to explain but I’m after that real traditional taste that used to make runner beans so moreish if you know what I mean