It was on BB, but it's too cool to not post again in case you missed it there: Bletchley Park's code competition for the garden monument at the Staffordshire estate.
"Knights Templar Academicals head up the League and provide what Bletchley Park's codebreakers believe to be the most rigorous attack on the mysterious message's defences. The analysis is a dissertation, passed to Bletchley Park's Director Christine Large following some esoteric historical research. The work was done in the mid-1990's by an American hobbyist based in the UK. It bears the mark of a codebreaking professional. The author, whose identity at present cannot be revealed, begins with an extensive and academically disciplined review of the monument's historical background, comprising almost all the themes subsequently researched by other would-be codebreakers. A thorough cipher analysis is then undertaken. Letter frequencies are done, decryption matrices tested to "bring out" the solution, indeed, all the conventional ways that key could be combined with plain (uncoded) text to form a cipher. The author then makes a number of assumptions about the Shugborough message, works out the matrices that would need to be anagrammed for possible plain text and decides to take a more specific approach, involving a shortcut. "
They're promising a site with more details of the mysterious "dissertation" and code breaking tips.