Charles I's Letters from the Isle of Wight Broken after Centuries

Some years ago, I presented three letters in cipher from Charles I to Prince Charles and another to Mr. Worsley in "King Charles II's Ciphers during Exile" and also included them in the list in "Unsolved Historical Ciphers". When Klaus Schmeh and Elonka Dunin chose them as one of the topics in their webinar, they found additional materials in the archives, which allowed Norbert Biermann and Matthew Brown to solve the cipher used in two of the four letters in my list. I presented their achievement in "What It Takes to Break Charles I's Cipher Used in the Isle of Wight".