Complex sentence: On the death of Sir John Juyn in 1440 he was appointed Chief Justice of the King's Bench, by patent dated 13 April 1440, which office he held for almost two years, his successor, Sir John Fortescue, being appointed on 25 January 1442.
Split into simpler sentences: On the death of Sir John Juyn in 1440 he was raised to the office of chief justice of the King's Bench, his patent being dated 13 April 1440. He held it not quite two years; his successor, Sir John Fortescue, being appointed on 25 January 1442.