This is the first critical edition of the Anglo-Saxon archive of the Benedictine monastery at Peterborough, established by Bishop Æthelwold around AD 970 on the site of an earlier house known as Medeshamstede. The archive comprises 31 documents ranging in date from the 7th to the 11th centuries. Alongside genuine royal diplomas, leases and an Old English will, are a series of spectacular forgeries that were created after the Norman Conquest as the monastic community strove to enhance its status and protect its endowment. A collection of hugely important memoranda, 'the Medeshamstede memoranda', preserve intriguing details of transactions that took place in the later 7th century, and a series of brief records illuminate the processes by which Æthelwold built up the endowment of the refounded abbey in the 970s and 980s. This volume contains authoritative editions of these 31 texts, plus a further 4 related documents. There is a full commentary on every text, with translation of all Old English documents and passages, and detailed discussion of boundary clauses. The Introduction provides a detailed elucidation of the history of the monastery in its two incarnations. This includes a ground-breaking new evaluation of the sources for the history of Medeshamstede, which overturns the conventional understanding of the status of this house and its supposed early 'colonies', and also much new material on the fate of this area of the East Midlands during the period in the 9th and early 10th centuries when it came under Danish rule. This volume will be of great value to those studying Anglo-Saxon and ecclesiastical history, to local historians, and to specialists in other fields, such as medieval Latin, Old English, and place-name studies.