Gray was the son of John de Gray, of Eaton in Norfolk and nephew of John de Gray, Bishop of Norwich. His birth year is not recorded, nor is his age when he died, but according to the historian Lee Wyatt, Gray was likely born around 1180. This assumes that in 1214 he was at least 30, the earliest legal age for consecration as a bishop, which would mean he was not born after 1184. Likewise, it is unlikely he was much older than 80 when he died, which gives an earliest possible birth year of 1175. He studied at Oxford University where he was tutored by Edmund of Abingdon. Gray was a favourite of King John of England, who appointed him Lord Chancellor in 1205, having paid John 5,000 marks for the office. He was named Bishop of Lichfield in 1210, but was never consecrated as bishop there. Gray was then elected Bishop of Worcester on 20 January 1214, after resigning as Chancellor in October 1214. His consecration as Bishop of Worcester took place on 5 October 1214. Gray was present at the signing of Magna Carta in June 1215. While he was away from England on a royal mission, he was appointed Archbishop of York, being elected on 10 November 1215 through the influence of John and Innocent III. John had wanted Walter, but the canons of York felt that Walter was ill-educated, and elected Simon Langton, brother of Stephen Langton, Archbishop of Canterbury. John objected, and wrote to Innocent III complaining of the election of the brother of one of his staunchest enemies, with which Innocent agreed. However, Gray eventually paid more than £10,000 to the Pope in various fees to get his election confirmed. Walter attended the Fourth Lateran Council in 1215. Gray was an important royal official during the minority of Henry III, who often posted him as a diplomatic envoy. Henry also named Gray as guardian of England when the King went to France in 1242. In 1252, Walter hosted King Henry and King Alexander III of Scotland for the Christmas feasts at York, which event cost the archbishop £2,500. Gray attempted to assert his archiepiscopal authority over Scotland, which not only resisted by the Scots but by the Archbishops of Canterbury. Gray had little success in defending his rights to Scotland against either adversary. Gray built the south transept of York Minster and purchased the village of Bishopthorpe, which became the residence of the Archbishop of York. He also endowed the church at Ripon. Gray held a series of councils in his diocese from 1241 to 1255 which endeavoured to enforce clerical celibacy, keep benefices from being inherited, and improve the education and morals of the clergy. He gave generously to his cathedral and other churches, as well as working to endow vicarages. He visited many of the monasteries of his diocese and helped those that were in financial difficulties. He also oversaw the translation of Wilfrid's remains to a new shrine at Ripon. Although Gray had absented himself from public businessfor a while, in 1255 he visited London to attend a meeting of parliament, and died at Fulham on 1 May 1255. He was buried on 15 May 1255 at York Minster. Three nephews of Gray would also be clerics: William Langton was Dean of York before being elected Archbishop of York but never consecrated, and Walter le Breton and Walter de Gray, who were canons of York.
