 On the day of the murder Grim was among a group who accompanied Becket into Canterbury Cathedral and stood by him during his altercation with the knights.He attempted to protect Becket from their attack until his own arm being nearly cut off by a stroke aimed at the primate, he fell to the ground but was able to crawl away to the altar where the archbishop's other clerks had hidden, and escaped with his life.His "Vita S. Thomas" cannot have been completed earlier than 1174 as it contains an account of the penance of Henry II; another passage seems to show that it was written not later than 1177 (Materials, ii.