Syon Abbey, established as the first Birgittine monastery in England in 1415, quite soon became a powerful institution within the order. Although often asserting their own conceptions of the Rule, the English Birgittines still sought the advice of Vadstena, their mother house, when it came to certain important matters concerning monastic life. The present work contains editions of two Latin texts: Responsiones, a document consisting of 175 questions and answers on the Birgittine Rule and daily life in the monastery, and Collacio, a sermon reflecting similar matters. The first part of the Responsiones consists of answers to five questions, sent from Syon to Sweden by letter. An important issue concerns the leadership in the monastery and the role of the Birgittine brothers. Were they to be seen as monks, living in their own monastery, or as religious assistans to the sisters? The second part was written as a direct result of two English brothers visiting Vadstena in 1427 and contains 170 questions and answers dealing with various matters of importance: how to interpret certain Birgittine texts, regulations on food, silence and speech as well as questions on preaching, liturgy and introduction into the monastery. The Collacio, in the manuscript said to have been presented to the Swedish community, was probably written by Syon’s conservator, the Benedictine abbot John Whethamstede of St Albans. Written in a highly metaphorical language rich in references to the Bible and Classical authors, the message to the Birgittine order is clear: first, it is wrong to have two leaders (confessor general as well as abbess) in one community; second, the Birgittines should strive to dispose of later additions and explanations and seek the original and true intentions of the foundress, Saint Birgitta. The thesis contains an introduction, editions with translations, glossary, indices, bibliography and plates.