Charters give lists of persons that attested the document and so it is possible to see who was present at the king's court. The very detailed diplomas drafted by the scribe known as "Æthelstan A" show that several Welsh kings, including Hywel Dda, attended the court of Æthelstan in the late 920s and the 930s. A person's absence from court can be equally revealing: Wulfstan I, Archbishop of York from 931 to 956, failed to attest any royal charters between 936 and 941, during which time the Battle of Brunanburh was fought between Æthelstan and an alliance of the Hiberno-Norse king of Dublin, Olaf Guthfrithson and the Scottish king, Constantine. Wulfstan was rather independently-minded and his absence from the West Saxon court can be linked with possible participation at Brunanburh and his later activity as a kind of kingmaker in York. It is also possible to trace a man's career at court through his position in the witness list, as in the case of Eadric Streona at the court of Æthelred 'the Unready' in the early 11th century.