Roald Dahl mentions in his childhood autobiography, Boy:

Cadbury’s were using some of the greatest chocolate-bar experts in the
world to test out their new inventions. We were of a sensible age,
between thirteen and eighteen, and we knew intimately every chocolate
bar in existence, from the Milk Flake to the Lemon Marshmallow. Quite
obviously our opinions on anything new would be valuable. All of us
entered into this game with great gusto, sitting in our studies and
nibbling each bar with the air of connoisseurs, giving our marks and
making our comments. “Too subtle for the common palate,” was one note
that I remember writing down.