of this process is that this took place in the 920s or 930s during the reign of King Athelstan. More recently, arguments have been given which places these changes in the reign of Alfred, possibly in the 890s in response to the new Viking invasions. Examples of this process can be seen in the replacement of Pilton by Barnstaple, and Halwell by Totnes and Kingsbridge in Devon. List of burhs This list shows the 33 burhs (with hidages) included in either or both of the 'A' and the 'B' groups of manuscripts as discussed by David Hill, in the order that they appear in all of the documents. Burhs that were probably added to the document group 'B' after Alfred's time are shown in bold. Comparison of the various manuscripts The Burgal Hidage survives in two versions of medieval and early modern date. Version A, Cotton Otho B.xi was badly damaged in a fire at Ashburnham House in 1731 but the body of the text survives thanks to a transcript made by the Tudor historian Laurence Nowell in 1562. Version B survives as a part of seven further manuscripts, usually given the title De numero hydarum Anglie in Britannia. There are several discrepancies in the lists recorded in the two versions of the document: Version A includes references to Burpham, Wareham and Bridport but omits Shaftesbury and Barnstaple which are listed in Version B. Version B also names Worcester and Warwick in an appended list. There have been some problems with the Nowell transcription. However modern scholars have compared Nowell's transcription of other manuscripts, where the originals are still available, enabling a picture of the conventions Nowell used to be built. This model was then applied in the correction of his transcription of the Burghal Hidage Ortho manuscript. It seems that Nowell did not understand the subtlety of the phonetics of the Anglo-Saxon written language and would therefore substitute, using his knowledge of Elizabethan grammar, what he saw as an equivalent letter, thus giving the Anglo-Saxon word a completely different sound and meaning. Other issues included for example, the original scribes' use of an open Old English "a" which Nowell incorrectly copied as a "u". The texts in the Version A and Cotton Otho B.xi are sufficiently similar to show that ultimately they do derive from one source. The historian David Hill shows how all of the recensions can be