CCCC MS 453 contains the Epistolae of Robert Grosseteste (d. 1253), bishop of Lincoln 1235-53, copied c. 1430. The letters are an invaluable source for the sometimes brutal ecclesiastical politics of the first half of the thirteenth century and the relationship between the papacy, national churches and the monarchy. It was surely this that made the codex of such interest to Parker, for whom such issues were very far from being mere historical curiosities. This manuscript served as the basis for what remains the only standard edition of Grosseteste's letters, that published for the Rolls Series by Luard in 1861.