Grisaunt as a young man taught philosophy at Oxford University, and in 1299 was either fellow or student of Merton College.
He incurred the suspicion of having practised magic, and when of mature age left England and studied medicine at Montpelier.
He afterwards settled at Marseilles, where he acquired great fame as a physician; he is said in his practice to have paid special attention to the nature and cause of the disease and to the constitution of the patient.
Grisaunt is commonly stated to have been the father of Grimoald or Grimoard (1309-1370), abbot of St. Victor at Marseilles, who became pope as Urban V in 1362.
According to Godwin, Anglic Grimoard is the cardinal John Anglicus, who was admitted dean of York 11 November 1366, and was deprived by the pope 1 May 1381 (Le Neve, Fasti, iii.