The British seem to be pretty confident they are the same apple and as per a discussion here awhile back RdR x 1700 and the KoP in Geneva have identical genetic markers meaning they are almost certainly genetically identical, and one scion came from England and the other came from France. There is another RdR in Geneva which is RdR x 82 and that may be the one you tasted, it is not the same as RdR x 1700 or KoP. See the discussion around here in this thread: Best tasting apples - #273 by scottfsmith.