Middenshire?

The team decided initially to take the letter at face value. William Thuck, who calls himself a 'Remembrancer' (a kind of record keeper or archivist), planned to take documentary evidence of 'Middenshire' (wherever that was) to God on Judgement Day, in order to counter an alleged act of treason supposedly perpetrated by the men of Middenshire against Henry the Fifth, who had made some decree concerning Middenshire's obscurity. This bald interpretation didn't help very much. What was the 'Dreadfull day of Doome' that Thuck had witnessed? What was this decree of Henry the Fifth? And where on earth was Middenshire?

Fortunately, the teams did not have to wait long for the answers to these questions. One particularly fat oilskin packet contained a thick unbound book, covered in handwritten notes, jottings and containing primitive woodcut illustrations. This book was entitled (using that economy of words for which the seventeenth century was justly famous):

A Perambulacion of ye entire countie of Midenshire, with a trew Historie of that place from ye earlyest dayes, and divers observacions concerning ye People, Townes and Antiquities therof, by Willm. Thuck, Printer.

The team could hardly believe what they were reading. Middenshire was an 'entire Countie', hitherto unknown. A quick perusal of the long and rambling introduction to the Perambulacion provided information on its location, and the reason why it was totally absent from every map and, indeed, from every single book on English history.