This study focuses on the problem of multilingual medieval text alignment, which presents specific challenges, due to the absence of modern punctuation in the texts and the non-standard forms of medieval languages. In order to perform the alignment of several witnesses from the multilingual tradition of the prose Lancelot, we first develop an automatic text segmenter based on BERT and then align the produced segments using Bertalign. This alignment is then used to produce stemmatological hypotheses, using phylogenetic methods. The aligned sequences are clustered independently by two human annotators and a clustering algorithm (DBScan), and the resulting variant tables submitted to maximum parsimony analysis, in order to produce trees. The trees are then compared and discussed in light of philological knowledge. Results tend to show that automatically clustered sequences can provide results comparable to those of human annotation.