BTW, Mildred, he has a chapter of his own in Horowitz, titled "Poniatowski keeps his locks"

Oh, good! Horowski (at least in part--I'm not committing to reading cover-to-cover) is on my list, either after or concurrently with Lehndorff (who in turns comes after the remaining Wilhelmine material and the very short Krockow volume on Heinrich and Fritz).