I could be wrong about this, but the D sound in British English (RP) sounds a little different from the American counterpart. Often when I hear the words "Lady", "Ready", "Hidden", or "I do", it has a tendency to sound very strong and breathy compared to how I would say it with an American accent. To me, it sounds similar to how a J would sound, but not exactly. I am aware that this definitely does not happen for all D-words, but I hear it often enough that it piqued my interest.
Was wondering if this is an actual phenomenon or if I am just hearing things. I heard that there are many variations in RP English, and that location and class can even affect it. Perhaps this way of pronouncing the D is specific to a certain variation?